Configure .htaccess for Google
There are always 2 version of your domain which are identical but uses different names.
The one with the .www and the one without.
For example:
1: http://www.marcuswestberg.com
2: http://marcuswestberg.com
It seems that both those adresses are the same, but Google looks at them in a different way.
When you receive links from people they link to your page with and without the .www, which ends up in different pagerank for your 2 versions of the domain name.
Now to the good part 
You can redirect so that only one version of your domain name receive all the pagerank from both adresses.
Add this piece of code to your .htaccess file
Options +FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} ^yourdomain\.com
RewriteRule ^(.*)$ http://www.yourdomain.com/$1 [R=permanent,L]
(Information in this article was taken from JW Webbdesign)
{ 2 comments… read them below or add one }
Didn’t know that… Seems like a good piece of information when opimizing my site
This approach will only work if mod_rewrite is installed on the server. Many hostings does not have it installed. If this is the case then try following approach: http://www.zubrag.com/articles/increasing-pagerank-google-sitemaps-webmaster-tools.php