Sub-Domains, Smart Choice?

By using sub-domains as part of your search engine marketing strategy, you may be able to increase the relevancy, keyword richness, and human appeal of your site’s pages. When done well, sub-domains offer several potential advantages over sub-directories. What’s the big difference? Let me explain.

Many sites separate their individual pages using sub-directories. This is how they appear:
http://www.site.com/optimize/page.htm

Sub-domains are also known as vanity names, machine names, or domain aliases. They are more concise than sub-directories and, therefore, easier for users to remember. The “www.” is replaced with a keyword that describes the page content. This is how they appear:
http://optimize.site.com

Sub-domains gain additional privilege compared to sub-directories because of their “top level” status. Most search engines will treat sub-domain URLs as a primary domain. This allows you to submit both your site’s domain and sub-domains as part of your search engine marketing strategy without being penalized. However, the content of each page must be unique for the multiple listings to be successfully indexed.

This search engine marketing strategy is especially useful to companies offering multiple products or services. Sub-domains help to tie your different offerings together by pairing page-specific keywords to your main domain name (i.e. http://sneakers.shoesrus.com; http://sandals.shoesrus.com; http://boots.shoesrus.com). By using descriptive keywords that you’re optimizing for in the URL, you add relevancy to your page. That is, search engines will rank your site more highly for that particular keyword. Users will also come to identify your company with that keyword, which can bolster your overall marketing and branding strategy.

Though sub-domains are being treated as unique domains, there is still debate going on about spammers abusing this privilege. Search engines may soon come up with clustering algorithms to counter the tricks.

Sub-Domain Spamming Controversy

Recently an industrious spammer noticed that Google's recent Big Daddy update has been giving undo credit to sub-domains. The spammer registered a few nonsense domain names, created literally millions of sub-domains on them, filled those sub-domain pages with nonsense content (mostly content scraped directly off of Google's search pages, mixed with random phrases and paragraphs likely pulled from article directories), got a bunch of links mostly from link-spamming blogs, then sat back while Google ate it all up.

In less than three weeks, the spammer had upwards of 5 BILLION pages indexed and ranking in Google, many generating profits by running Google AdSense. The pages were gibberish, and they were hosted on mostly gibberish domains. That didn't stop them from ranking well for a huge number of search queries. Once this spam attack was exposed on tech sites like Digg.com, Google got wind of it and we could actually watch the number of indexed pages drop before our eyes, from 5 billion to 4 billion to 3 billion, and eventually down to almost nothing.

The interesting part about spam these days is that everyone uses it to make money from Adsense. So, this person probably made a lot of money very quickly with this strategy and Google may owe them a big chunk of money. In light of this incident, you can be certain that the search engines will be more careful from now on when it comes to sub-domains.

Sub-Domains and SEM Strategy
To get the most out of sub-domains without incurring any penalties, make sure you don't create a sub-domain when there isn't a good user focused reason to do so. Avoid having sub-domains with only one or two pages on them—a small number of pages on a sub-domain (other than www.) is a red flag to a search engine. You can expect that ranking penalties or outright bans could be levied on any site that combines the typical www.domain.com format with a bunch of low-populated keyword-laced sub-domains in an obvious effort to manipulate rankings.

At this time, sub-domains continue to provide increased visitor traffic and can improve your site’s relevancy with the search engines. Even if your site won’t be switching from sub-directories to sub-domains right away, it’s a smart move to register the keyword-rich URLs now so they’ll be available down the road. We will continue to monitor the search engines to see how the sub-domain controversy plays out, so keep your eyes on our blog for future updates.