The entire domain’s authority and trust is reflected by this page rank value. The home page then tends to distribute this page rank to the first level (categories), the second level (sub-categories) and the third level product pages which we often refer to as link juice. In general, the first level pages tend to derive the maximum link juice from the home page. But in a site with excessive number of sub-categories and product pages (money pages), the pagerank distribution is not proportional with some gaining link juice and a large majority not gaining any.

I am not delving into pagerank sculpting which was the rage of the SEO industry not long ago. This method was adopted to make certain areas of a site more powerful by flowing link juice from the home page preferentially to pages of interest (possible commercial intent). The internal linking architecture is altered from its natural form to highlight more important pages than the rest on the site.

In my opinion, internal linking with appropriate anchor text can be used to improve the ranking of pages within a site but this has its limitations. Integrating a blog with the main site so that it forms part of the global site template is vital. The different posts on the site blog can point to different pages of the site to flow some much needed link juice to prop select pages up and assist them in getting indexed by Google and ranked on the SERPs.

Eric Enge at Stone Temple Consulting has done some research in regards to distribution of domain authority and trust to pages on the lower level pages of a site. Let us assume you have a site selling products. You have the home page, many categories with respective sub-categories and product pages in that order. Let us consider an example where you sell Canon digital cameras as shown below.

The specific product page in question is listed on Page 4. You are not happy as this product page has not recorded any page rank. If it does not have the requisite page rank, there is a possibility that it will not gain entry into the Google index.

In this scenario, it is evident that the site despite a great PR of 6 is not able to flow link juice into this specific product page. Eric has found out in his experiments that an inbbound link to this deep page with appropriate anchor text (in this case EOS D7 Canon Digital Camera Review) from an external site is a huge help to get this product page into the index and help get it ranked. The link may not be of superior quality yet it helps a great deal.

As we all know, every inbound link is a vote to the site and the search engines recognise this as a strong signal. The search engines adjust their algorithm accordingly to flow more internal link juice into the page which has gained inbouind links. The more the merrier seems to be the case.

In our example, the Canon EOS D7 product page ends up gaining link juice thus helping it enter the Google index and get ranked over time. Deep inbound links help a site distribute more authority and trust to pages that receive such inbound links. This is a classic case of an inbound link triggering a tunnel of sorts to flow a site’s internal link juice to select pages at a lower hierarchy level.

In summary, you do not need masses of links to get your third level or product pages indexed and ranked on the SERPs. Just a few inbound links will facilitate better flow of the site’s domain authority and trust (read link juice) to the specific page recipient of the inbound links in question. You can read the post on impact of deep inbound links on a site’s lower level pages on Eric’s site.

Ravi Venkatesan is a senior SEO consultant at Netconcepts, an Auckland search engine marketing company offering both seo and pay per click services to their customers in New Zealand and Australia.

Can you keep a secret? There is an unfair advantage. Amazon is applying conditional 301 URL redirects through their massive affiliate marketing program.

Most online merchants outsource the management and administration of their affiliate program to a provider who tracks all affiliate activity, using special tracking URLs. These URLs typically break the link association between affiliate and merchant site pages. As a result, most natural search traffic comes from brand related keywords, as opposed to long tail keywords. Most merchants can only imagine the sudden natural search boost they’d get from their tens of thousands of existing affiliate sites deeply linking to their website pages with great anchor text. But not Amazon!

Amazon’s affiliate (“associate”) program is fully integrated into the website. So the URL that you get by clicking from Guy Kawasaki’s blog for example to buy one of his favorite books from Amazon doesn’t route you through a third party tracking URL, as would be the case with most merchant affilate programs. Instead, you’ll find it links to an Amazon.com URL (to be precise: http://www.amazon.com/exec/obidos/ASIN/0060521996/guykawasakico-20), with the notable associate’s name at the end of the URL so Guy can earn his commission.

However, refresh that page with your browser’s Googlebot User Agent detection turned on, and you’ll see what Googlebot (and others) get when they request that same URL: http://www.amazon.com/Innovators-Dilemma-Revolutionary-Business-Essentials/dp/0060521996 delivered via a 301 redirect script. That’s the same URL that shows up in Google when you search for this book title.

So if you are a human coming in from affiliate land, you get one URL used to track your referrer’s commission. If you are a bot visiting this URL, you are told these URLs now redirect to the keyword URLs. In this way, Amazon is able to have its cake and eat it too – provide an owned and operated affiliate management system while harvesting the PageRank from millions of deep affiliate backlinks to maximize their ranking visibility in your long tail search query.

(Note I’ve abstained from hyperlinking these URLs so bots crawling this content do not further entrench Amazon’s ranking on these URLs, although they are already #4 in the query above!).

So is this strategy ethical? Conditional redirects are a no-no because it sends mixed signals to the engine – is the URL permanently moved or not? If it is, but only for bots, then you are crossing the SEO line. But in Amazon’s case it appears searchers as well as general site users also get the keyword URL, so it is merely the affiliate users that get an “old” URL. If that’s the case across the board, it would be difficult to argue Amazon is abusing this concept, but rather have cleverly engineered a solution to a visibility problem that other merchants would replicate if they could. In fact, from a searcher perspective, were it not for Amazon, many long tail product queries consumers conduct would return zero recognizable retail brands to buy from, with all due respect to PriceGrabber, DealTime, BizRate, NexTag, and eBay.

As a result of this long tail strategy, I’d speculate that Amazon’s natural search keyword traffic distribution looks more like 40/60 brand to non-brand, rather than the typical 80/20 or 90/10 distribution curve most merchants (who lack affiliate search benefits) receive.

Brian

As you may recall, I’ve written before about how dealer locators are terribly optimized and how store locator pages can be optimized. A great many store locator sections of major corporate sites are not allowing search engine spiders to properly crawl through and index all the locations where they may have brick-and-mortar outlets.

Most large companies seem fairly unaware that their store locators are effectively blocking search engine spiders and are making it impossible for endusers to find their locations through simple keyword searches. I’ve also listed out a number of top store locator providers which produce locational services like this for many Internet Retailer 500 companies.

Read on for details on our results…

In the last two months, we’ve optimized the store locator sections of two different GravityStream client sites, resulting in major improvements in rankings and traffic for both.

For client #1, their store locator section was already moderately passable for search in the sense that they’d constructed the section so that spiders could easily crawl through and index their pages. However, they’d failed to really tweak the individual page elements that could “sing to the search engines” about what the pages’ core content was really about. For instance, the Titles and H1s of the pages were all identical for all the various locations where they have stores across the country, and some of the page content was ineffectual, such as a lack of good Meta descriptions and image ALT content.

We fixed all those items, making each store profile page uniquely titled to make it apparent to the search engines as to what the content was about, and we further kicked it up a notch by rendering the store address and phone content in hCard Microformats.

The results were fantastic!  In 136 local search combination queries, these store locator pages improved in their rankings in 80 of the queries. (This company only has about 30 locations in the US market.) The majority of the improvement was in rankings in Yahoo! and Microsoft Live searches — this is primarily because their pages were already ranking well in Google (#1 position in most cases), apparently due to Google’s superior capability at identifying authoritative content and associating it with the keyword search terms effectively.

But, in 11 cases, our changes allowed the company’s store pages to move up in Google’s SERPs, too, popping into position #1.

Some of the ranking improvements were very dramatic, allowing the site’s pages to improve in rankings by anywhere from 10 to 20+ positions.

The test search combinations were typical searches that consumers could be expected to make when looking for this company’s stores, using the company’s brandname:

• BrandX in Dallas
• BrandX Dallas, Tx
• Dallas BrandX
• BrandX Texas
• BrandX in Texas

This particular company has a fairly well-known brand name, making it natural for users to search for the store by tacking locality parameters into the search phrase when looking for the store locations. Also, it’s our general philosophy that companies with unique brand names can and should be able to rank well for their brand name searches, and our results as shown by these test queries back this up.

For client #2, the GravityStream optimization of their store locator pages was even more dramatic.

Client #2 is a very well-known nationwide retailer with stores in most major metro areas, and their store locator section, provided by a third-party, was constructed in such a way as to bar any of their dealer location pages from being indexed at all. (The location pages were all behind a search form, which is one of the all-time classic major barricades to search engine spiders.)

Through GravityStream, we created a linking structure to expose the content, and generated location pages for 107 cities in the US with optimal formatting. This is just the beginning for this client, however, since they have many more locations available. But, we wished to ramp them up slowly to insure a natural progression and to iron out any potential kinks before widening to expose more content.

We tested on 107 representative local queries (similar to client #1, we searched for combinations like “BrandX in Boston MA”).

Only a small fraction (about 4) of the pages have been slower to get crawled/indexed, so client #2 now has about a hundred pages showing up in SERPs which they’ve never had exposed before.

• 47 of the search queries put the new store locator pages in Position 1 in Google!
• 83 of the search queries put the new pages on Page 1 of Google results!
• This company’s pages are in a great many cases now outranking top yellow pages company pages and other retail directory pages which were previously the only pages representing their brand for local search queries.
• Although this company does submit a feed to Google Maps, there were a number of common local search queries where Maps results didn’t appear in the onebox on the results page, as one might otherwise expect under Universal Search. This indicates that organic SERP listings continue to be a necessity in many cases.

Achieving position number one for many keyword searches where you’ve never enjoyed rankings whatsoever is just the sort of thing we like providing to our clients.

Our GravityStream system is provided as a sort of web service to companies. Large, complex sites partner with us by installing proxy code on their server, allowing GravityStream to dynamically fix technical elements and to inject human-tweaked keyword content to insure best potential for ranking in search engine results.

Unlike many search marketing firms, we are so confident of our work that we charge clients based on the number of clickthroughs we drive to them from search engines, and we discount their brand name keywords on the assumption that they should be already getting their branded search traffic already without our assistance.

Those of us cooking up cool functionality in the GravityStream labs have even more stuff that we’ll be deploying on behalf of our clients this year, so stay tuned for more developments.

Not long ago, I wrote an article on how some local directory sites were using subdomains in an attempt to achieve good ranking results in search engines. In that article, I concluded that most of these sites were ranking well for other reasons not directly related to the presence of the keyword as a subdomain — I showed some examples of sites which ranked equally well or better in many cases where the keyword was a part of the URI as opposed to the subdomain. So, in Google, subdirectories were already functioning just as well as subdomains for the purposes of keyword rank optimization.

I’ve seen a lot of sites which had varying degrees of quality in their subdomaining strategies. If you do have subdomains, you should ideally insure that they contain primarily unique content not reflected on your other domains — each subdomain should contain page content that does not also live on other subdomains or else it can appear that you are attempting to spam the search engine indices.

Google’s Webmaster Guidelines are very clear on this subject:

“Don’t create multiple pages, subdomains, or domains with substantially duplicate content.”

Most large corporate websites have some level of accidental duplicate content, but if you deploy dozens or hundreds of subdomains with all dupe text, it will appear that you’re purposefully trying to spam the search engines — don’t do it.

If you are considering how to structure your URLs and site content for natural search marketing, I’d say you might be better off just using a simple format of descriptively keyworded directories and subdirectories rather than keyworded subdomains. This is often easier to manage, and it looks a lot more natural/reasonable from the search engines’ perspective. There’s lower likelihood of accidentally mirroring/duplicating your content, too.

Don’t freak out if you have a few subdomains — this is also natural. Many major websites host different site sections and applications on subdomains, and some have external providers delivering content on separate servers — it’s very easy in those cases to assign a subdomain to the third party that’s providing service for you. As long as you’re not duplicating the main content of your pages on the subdomains, this is fine.
Finally, I’ve had a number of people ask my opinion regarding foreign languages — which is better, subdomain or subdirectory.

I actually prefer using separate top-level domains (“TLDs”) for this purpose, since it allows you to send a very clear signal to the search engines that particular content is intended for various countries. For instance, your French language pages could be delivered on .FR domains like: www.example.fr

However, if for some reason you don’t wish to use foreign TLDs for your alternate language pages, you should not worry overly about using separate subdomains versus directory/subdirectories. “french.example.com” will likely function just as well as “www.example.com/french/” in my opinion. I believe that translated versions of pages are NOT counted as duplicate content because they essentially contain very different text. Yes, the information may be duplicated, but the text content is not, and pages in two different languages are far less likely to both come us as relevent for the same keyword search.

So, for foreign language pages, I recommend separate TLDs for best performance, or else use whatever approach is easiest for you to set up and maintain.

For many national or regional chain stores, providing dealer-locator services with robust maps, driving directions and proximity search capability is outside of their core competencies, and they frequently choose to outsource that development work or purchase software to enable the service easily.

I did a quick survey and found a number of companies providing dealer locator or store finder functionality:

Bullseye Integrated Locator Solutions

CMC International

Flattext Database Scripts

Got WWW Store Locator

InfoNow

Know-Where Systems

SmartLocator.com

Source Software, Inc

SpatialPoint

Tetrad

Where2GetIt

Xtreme LocatorUltimate Locator

Zenoweb Locator

ZipMath Software

Some of these services are relatively simple applications using the APIs provided by the big mapping vendors while others have custom-built their applications from the ground up.

As far as I can tell, none of these services or software solutions have built their applications to be search engine friendly as I described in my article on SEO for Store Locators. It’s not all that hard to build web applications to be optimal, but it does require that application developers understand the need and modify the format of their applications to satisfy the additional criteria, and it requires someone who’s familiar with search optimization to specify the needed changes.

Considering the amount of competition among store locator providers, perhaps some will now choose to better differentiate themselves from the crowd by re-engineering their applications to allow search engine spiders to crawl through their content and index their pages.

And, any major corporation should turn to their service providers and insist that they adjust their applications to facilitate local search optimization.

UPDATE 1/8/2008: We have now begun providing local search optimization through our GravityStream product. Check out the details: GravityStream Optimizes Store Locator Pages.

Maile suggests a few ways of addressing dupe content, and she also reveals a few details of Google’s workings that are interesting, including:

• Unnecessarily long URLs are unattractive, and might reduce chances that a user would click through to your page. While this sounds like a subjective opinion that’s a bit counter-intuitive (because one could assume that users focus more on link titles than length of URLs), it’s quite possible that Google would have done enough experimentation during their usability testing to know for sure that longer URLs might actually have a negative impact on click-through rates. So, avoid longer URLs if possible in your application design!
• When deciding what to display from your site for a user’s search, if Google detects duplicate content matching the user’s query, they’ll group all the dupe pages into a cluster, and then apply some methods to choose which of your pages would be the best choice to present to their searcher.
• They attempt to focus the collective “link popularity” or PageRank from all members of a cluster on your site to one page. This is slightly odd, since it runs counter to her earlier statement that duplication can cause “link popularity” dilution. Likely, this means that there are cases when Google can find it difficult to cluster all dupes from a site, so it’s still best to reduce duplication rather than solely rely upon their algorithms to handle it for you.
• She suggests using a Sitemap to inform them of the primary URLs of a site, which suggests that Google may be using the sitemaps as a prime indicator when trying to select a canonical URL for a particular cluster. I note that while using a sitemap could help Google select which of your dupe pages to present to a user, it doesn’t really solve your entire dupe problem — you should still try to use additional methods to manage dupes.

Maile’s suggestions reiterate some of the de-duplication advice I’ve previously given, and I’ve also suggested having your site resolve to a single domain name to reduce duplication (along with Google’s Matt Cutts, who also recommends domain canonicalization).

Each of the search engines handle duplication issues a little differently, making it desirable to use best practices to manage the issue, if you really want to improve your site’s natural search performance.

GravityStream is a technical solution that provides outsourced search optimization to large, dynamic websites. Automatic SEO, if you will. Here’s what it does…

A lot of major sites out there have difficulty optimizing themselves to improve rankings in search engine results pages (“SERPs”) in order to increase their organic traffic. It requires a unique mixture of conditions to do SEO: an expert who can diagnose all the structural factors that block spidering; programmers and system administrators who can make all the changes recommended by the expert; statisticians who can interpret the web metrics to monitor the impact of changes; writers and taxonomy specialists who can perform keyword optimizations; and, strategic analysts who can find new advantages to exploit.

Most companies don’t have all the necessary capabilities on-staff to do optimization fully in-house, and many companies continue to ignore their natural search marketing in favor of less-complex initiatives. Yesterday, I analyzed the product catalog of Coca-Cola’s online store as a representative example of the sorts of problems internet retail sites have, and outlined a number of factors that they would need to improve in order to rank ideally for all the various search terms their products should be targeting/ranking for. Coca-Cola’s not unique in overlooking proper use of the common signals for search optimization.

Online retail sites frequently share a number of nonoptimal characteristics including:

• Title tags not uniquely formulated for each page;
• Non-unique or non-existant META Description tags;
• Sitewide navigation dependent upon Flash/Java/Javascript applications such as commonly found in dynamic menus;
• Non-unique or nonexistant H1 tags;
• Lack of link hierarchy exposing all pages to search engine spiders;
• Internal links using worthless terms in link text;
• Category nomenclature using keywords which don’t perform well;
• Page URLs containing stop characters which block spidering;
• Page URLs too lengthy;
• User session IDs parsed into page URLs, causing massive duplicaton;
• Page URLs do not include keywords;
• Insufficient text content on pages and image-only page content;
• Image tags not containing valuable ALT text parameter;
• Pages too tightly focused on keywords instead of including a few additional terms to enhance traffic;

So, why don’t companies address these issues? Many companies are missing one or more of the resources needed to handle everything internally. But, even those companies which bring in external consultants to provide SEO guidance do not accomplish all the most-basic optimization elements. It’s well known throughout the search marketing industry that companies often don’t implement the recommendations of search agencies. Most companies are very like big families – dysfunctional to some degree. The marketing managers who understand what needs to be done cannot get the IT resources to cooperate, and it’s hard to keep the focus needed to make sure all the optimizations are executed and maintained.

Even the companies which have awakened to the potential of search marketing and have staffed up to develop optimizations in-house may have substantial delays before they can deploy needed changes, due to the sometimes lengthy development cycles of major corporations or lack of coordination between development teams.

GravityStream was created to fill this gap, providing a near-turn-key solution to automatically optimize large dynamic sites quicker and more comprehensively than companies can do in-house, at a fraction of the cost in staffing up and developing the work. GravityStream can address all the problems outlined in the above list, correcting sites’ pages and delivering them up to the search engines in optimized format.

How does it do it? GravityStream is a solution which allows us to proxy a client’s website by taking the native site pages, dynamically processing them to improve multiple factors such as TITLEs, H1s, META tags, etc – and then we deliver the page back through the client’s own domain name. In order for us to integrate with a client’s site, we ask the client’s system administrators to install a few rewrite rules on the server which send various page requests over to GravityStream to process. We replace core content links when search engine bots visit the site, generating hyperlinks which the rewrite rules can identify and cede over to GravityStream for processing.

One common question we get with clients is whether GravityStream’s process is a type of cloaking. The answer is no! Cloaking is defined as an effort to deceive search engines by delivering up content that appears different to spiders than it does to humans. GravityStream delivers up the same content to users as to search engine spiders for a URL, except the hyperlinks are formatted differently.

For instance, one reason we clean up and rewrite URLs is to remove things like Session IDs which cause heartburn for search engines. Managing URL formats to resolve indexation issues is allowed under Google’s Webmaster Guidelines, and follows their recommended best practices. Under their Technical Guidelines, Google states:

“Allow search bots to crawl your sites without session IDs or arguments that track their path through the site. These techniques are useful for tracking individual user behavior, but the access pattern of bots is entirely different. Using these techniques may result in incomplete indexing of your site, as bots may not be able to eliminate URLs that look different but actually point to the same page.”

By working with a client’s application engineers, Netconcepts technicians can enable Google, Yahoo!, Microsoft Live and Ask to crawl a site without the pesky Session IDs, and with shorter URLs which include valuable keywords in them. Once an enduser arrives on the GravityStream formatted page, the hyperlinks revert back to the native site’s format, allowing all tracking and user-experience management methods to be used as normal.

GravityStream doesn’t have to be purely automatic/algorithmic. The GravityStream system also provides administrative interfaces which allow our taxonomy/keyword optimization specialists to inject keyword-rich text into client site pages, and allows them to hand-tweak TITLEs and other page signals as needed. For clients with in-house copy-writing staff, the admin interfaces can be used for hands-on content management so custom optimization can be easily accomplished by their own employees.

The system also provides performance monitoring tools and metrics on how much traffic is produced through the GravityStream pages, as well as information on indexing and keyword referrals.

Netconcepts has a couple of pricing models available to clients, one of which is particularly innovative in the search optimization industry: Pay Per Click! On this pricing model, the client is charged for the amount of traffic that the GravityStreamed pages bring to the site, and we do not charge for certain client brand name referrals such as the company name. How many other search optimization firms offer a pricing model based upon actual performance of their work?

GravityStream has provided best-in-class optimization work for a number of Fortune 500 companies and top most-recognized brand retail sites. Various news reports have also mentioned GravityStream’s success on behalf of clients, though some of our best success stories are kept confidential at the request of the companies involved.

I found the GravityStream product and success very compelling when I was considering joining Netconcepts, and I now  recommend the product for firms with enterprise-class, top retail sites in particular. GravityStream functions very similarly to a system I designed when in-house at my former company, where I had built an application which proxied a legacy site application in order to optimize our own pages more rapidly/easily. So, GravityStream has a basic approach which in my experience functions quite well.

Most companies may want to perform SEO in-house at some future point, but there’s typically a considerable delay between initiating efforts to staff up and work through a project plan to get everything optimal. For some clients, GravityStream has been a solution for bridging them over between their current non-optimal state and the future point where they’re ready to do it all on through their native site. It’s valuable to recognize that failing to optimize sooner will represent some lost market share and money left on the table in the here and now. With change happening so rapidly in the internet space, it’s vital to grab as much market share as possible, as early as possible. GravityStream is a way to get optimized rapidly – we typically can schedule and deploy GravityStream within about six weeks of contract signature.

GravityStream is still evolving, too. We’re working on a lot of new features which will benefit all of our clients using the service. While many companies have some search marketing managers in-house, most do not have the benefit of a broadly experienced staff performing cutting-edge research and development in natural search optimization. Contracting for GravityStream can instantly provide the benefit of a completely staffed department of specialists who know search optimization.

If you’re interested in what GravityStream could do for your site, contact one of our business development representatives at (888) 207-1109, or contact us online.

• CitySearch
• Craigslist
• Local.com

In that installment, I conclude that the subdomaining for the sake of keyword ranking has no real benefit.

This assertion really can be extended out to all other types of sites as well, since the ranking criteria that the search engines use is not limited to only local info sites. Keywords in subdomains really have no major benefit.

SEO firms used to suggest that people deploy their content out onto “microsites” for all their keywords – a different domain name to target each one. This just isn’t a good strategy, really. Focus on improving the quality of content for each keyword, founded on its own page, and work on your link-building efforts (quality link-building, not unqualified bad-quality links). Tons of keyword domains or subdomains is no quick solution for ranking well.

Download/Listen:

• Neil Patel interview (15 minute MP3, 3 megs) – getting to the front page of Digg and other social media sites
• Eric Ward interview (36 minute MP3, 8 megs) – tips and secrets on how to garner links
• Vanessa Fox interview (40 minute MP3, 9 megs) – Google’s webmaster tools, SEO impacts of AJAX, Flash, duplicate content, redirects, etc.

More podcasts to come from other speakers, so be sure to subscribe to the RSS feed so you don’t miss them. Also be sure to register for the conference at one of the three cities, it’ll be great!

Read on to see what I mean.

Sure she’s right in that webmasters don’t have to be afraid if their applications have created multiple page URLs which all contain identical or near-identical content. Websites do this all the time, and search engines aren’t penalizing them for it. (Except perhaps for the case of page-scrapers who steal other sites’ content for redisplay — in which case a scraper’s page might get penalized or just ranked lower as being non-authoritative for its content.) But, webmasters *do* still need to be concerned with duplicate content, because it can affect their overall traffic and rankings.

Quite simply, PageRank continues to be one big factor in ranking one page versus another for keyword searches. Most sites only have so much PageRank to spend on all the pages in their site. If you double the number of pages on your site, you may be virtually cutting each page’s PageRank in half when you do it. If you deploy duplicate copies of all your pages willy-nilly, you’ll have watered-down your pages’ PageRank scores for no good reason.

I wish Jill had mentioned this — dupe content may not cause a website to be penalized, but it’s still an important factor for the sake of improving/optimizing a site’s pages to rank better and bring in more traffic. Her article seems to leave one with the feeling that since there’s not a penalization, webmasters just don’t need to worry about duplication at all.

I say, what do webmasters care if it’s called “penalization” or not, if the end result is still unnecessarily lower rankings in SERPs?                             

If you don’t know what duplicate content may be, you should know that there are a number of things which can cause it to occur in web applications. Primarily, if you have multiple different URLs which all present the same page content, and all of these URLs can be found and indexed by search engine spiders, then you have a duplicate content problem. Here’s some common examples:

• http://example.com & http://www.example.com both present pages for users. As the homepage of your site, if both are indexed by search engines with no qualification, they effectively will split your homepage PR. If subpages are also indexed on both domains, it splits the PR of any of those pages on your site, too. You need one, canonical (i.e. “official”) domain for your site.
    
• http://www.example.com/index.html is the same as http://www.example.com/ — if your site developers linked to the homepage indescriminantly, using both of these types of URLs, they’ve split your homepage’s PageRank.
    
• http://www.example.com/?UID=A7WF5681HJF145I — if your site uses sessionizing in ubiquitous querystrings — assigning session IDs for users for personalization and such — there could be hundreds of different URLs indexed for pages, causing loads of PageRank split through duplication.
    
• www.example.com/app.jsp?DATE=3/17/07&PageID=6 is the same as:
  www.example.com/app.jsp?PageID=6&DATE=3/17/07 and the same as:
  www.example.com/app.jsp?PageID=6&DATE=3/17/07&Link=ad
  - if a page’s URL has multiple querystring terms and different links point into it with the terms in different order, it can create duplication.

These are just some examples — there are many more cases possible.

There are a handful of ways you can fight duplication problems or mitigate their effects on PageRank:

• Fix your site/application so that only one URL per page of content will occur or be found by spiders;
    
• Make the application deliver up NOINDEX metatags for alternate page URLs;
    
• Move user session IDs out of page querystrings and into persistent cookies;
    
• Place 301 redirects on alternative page URLs, redirecting over to the permanant, primary page URL;
    
• If setting up special querystringed page URLs for tracking media campaigns, place those URLs in a special subdirectory on your site which you’ve specified in your robots.txt file for search engines to not index;

There are a number of other solutions out there, depending upon what your duplication problem may be. In most cases, fixing duplication is going to be a bit of a technical clean-up job, but the benefit to your overall page rankings and referral traffic may be significant.

You don’t need to worry about being “penalized” for duplicate content within your site — you’re not going to be delisted for it. But *do* worry about how it affects the SERP rankings for your content.