You should decide whether the www or non-www version is you canonical (preferred) version of your site’s URLs and 301 redirect the non-canonical version of all URLs to their corresponding canonical version of the URL. If your site is hosted on an Apache web server, this is as simple as adding a single RewriteRule in the .htaccess located in the root folder of your web.

For example, if you want the non-www version of your URLs to be the canonical form of your URLs then the following would do the trick:

RewriteCond %{HTTP_HOST} ^www.example.com$ [NC]
RewriteRule (.*) http://example.com/$1 [R=301,L]

If you want the www version of your URLs to be the canonical form of your URLs then the following should work:

RewriteCond %{HTTP_HOST} ^example.com$ [NC]
RewriteRule (.*) http://www.example.com/$1 [R=301,L]

The above will fix your URL canonicalization issues for ALL search engines.

Also, you can fix it just for Google quite easily. Once you’ve verified both the www and non-www versions of your site, once logged into Webmaster Tools, go to Site Configuration -> Settings and select your Preferred Domain.

Fixing URL canonicalization issues using 301 redirects is the preferred way because it corrects the problems across all engines, but if you don’t have the tools or skills to implement the 301 redirects then fixing it with Webmaster Tools is the next best thing.

Sharon

Most people typically verify two versions of their site – the www and non-www version. Once you get one verified (using the meta tag or HTML file method) all you have to do is ADD the other site in WMT and press the verify button. In 99.999% of the cases it will verify immediately unless you’re doing something “funky” in code so that you’re not rendering the same home page for both (meta tags are different) or somehow the DNS for the www and non-www resolve to different folders on your web server. If you want to set the preferred domain (www or non-www) in WMT then you have to verify both the www and non-www version of the domain. So page name, font, case, etc. really have no bearing on verification because people typically verify their domains.

One little known fact, however, that most people don’t know… you CAN verify a file on your site. Say I’ve verified http://www.example.com and example.com and I’ve set my preferred domain to http://www.example.com... I can also add http://www.example.com/some-folder/ and verify it. This will automatically verify as well (assuming you’ve already verified http://www.example.com). This will allow you to get information specifically about the http://www.example.com/some-folder/ section of the site (that page and all pages that live under it like http://www.example.com/some-folder/some-sub-folder/page-name.html). You’ll notice when you do this a lot of the info in WMT for that “section” of the site are blank because they are real “site” level information… but a lot of the info is there and adjusted so that it is only about that “section” of the site.