"How to Get Credit for All Your Inbound Links - Consolidate WWW and non-WWW Links"
Strangely enough, the following addresses are considered separate websites by the search engines:
http://www.yourdomain.com (the "www" version)
http://yourdomain.com (the "non-www" version)
Though visitors see the same content, in the search engine world this situation poses a serious issue relating to link popularity. If the "www" version of your website has 300 inbound links and the "non-www" version has 300 inbound links, then each version is getting credit for only 300 links rather than the total 600.
Here are some immediate steps you can take to minimize the problem:
I recommend the "www" version because this seems to be the most common method used to type in an address. If you agree, use the format http://www.yourdomain.com on every link you can control.
Review your website and fix any links that use the "non-www" version. For example, if you have a link on every page back to your homepage and it uses the non-www format, switch it to the www-format.
Fix What You Can Offsite.
Repair any offsite links that may be directing traffic to your website using the wrong version of your address. If you have partnerships with other websites or advertising campaigns that use the wrong URL, ask them to change the links where possible.
Remove the Problem Entirely.
Next minimize the damage of incorrect backlinks from any other sites by having your webserver "tell" the search engines that the non-www URL is now permanently redirected to the www-version.
After you do this, if someone types in or clicks on a non-www version URL, they'll be automatically redirected to the proper www-version URL. Best of all, search engines interpret this redirect positively and will forward all link popularity to the www-version URL.
Consequently, you will have consolidated the popularity from both URLs into a single website which can significantly increase link popularity and search engine rankings.
Implementing this "server-side 301 redirect" will require the aid of a technical person comfortable with making website alterations. Refer your technical aide to the following tutorial:
"How to 301 Redirect Non-WWW to WWW URLs" (www.stepforth.com/faq/non-www-redirect.htm).
Google offers a feature in Google Webmaster Tools (www.google.com/webmasters/tools/) that allows you to tell Google which version of your domain to use within the Google search engine.
You'll need to login to an existing account or create a free one for your site. Once you verify that you control the domain, on the Webmaster Tools My Sites page, click on the link to "Manage http://yourdomain.com". In the left navigation menu go to Tools > Preferred domain to make your selection. Realize, however, that is a Google-only work-around and not a fix. It's far better to implement the 301 redirect described above which corrects the problem for all search engines.
Once you've consolidated the value of all the links pointed to your site you are another step closer to securing better search engine rankings.
Source: Ross Dunn, CEO StepForth SEO Services