Well i used to have the problem in it the ranking of one form which might be any www or without www to be of better page rank then the other one.IF it happens to you then the simple solution is to redirect the url with 301

Here is how to do it

Redirect to www (htaccess redirect)

Create a .htaccess file with the below code, it will ensure that all requests coming in to domain.com will get redirected to www.domain.com
The .htaccess file needs to be placed in the root directory of your old website (i.e the same directory where your index file is placed)

Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^domain.com [nc]
rewriterule ^(.*)$ http://www.domain.com/$1 [r=301,nc]

Please REPLACE domain.com and www.newdomain.com with your actual domain name.

Note* This .htaccess method of redirection works ONLY on Linux servers having the Apache Mod-Rewrite moduled enabled.

Don’t forget to check it

You can Test your redirection with Search Engine Friendly Redirect Checker

http://www.webconfs.com/redirect-check.php