Take a few seconds to look at the following URLs:

* http://www.yourdomain.com
* http://yourdomain.com
* http://www.yourdomain.com/index.php
* http://www.yourdomain.com/index.html
* http://yourdomain.com/index.php
* http://yourdomain.com/index.html

On the long run you’ll see that that each of the above URLs will have different backlinks and PR. That is because your site is suffering from URL Canonicalization!
Most probably the PR will be low.

So it is best that you get all the links on to any one URL.

By doing this you will optimize all the SEO work you have put in.

Just adding these lines to your .htaccess will solve the problem.

Redirect a http://yourdomain.com to http://www.yourdomain.com:

RewriteEngine on
RewriteCond %(HTTP_HOST) ^yourdomain.com
RewriteRule (.*) http://www.yourdomain.com/$1 [R=301,L]
Redirect your http://www.yourdomain.com/index.php to http://www.yourdomain.com:

RewriteEngine on
RewriteCond %(THE_REQUEST) ^[A-Z] {3,9}\ /.*index\.php\ HTTP/
RewriteRule (.*) index\.php$ /$1 [R=301,L]
Redirect your http://www.yourdomain.com/index.html to http://www.yourdomain.com:

RewriteEngine on
RewriteCond %(THE_REQUEST) ^[A-Z] {3,9}\ /.*index\.html\ HTTP/
RewriteRule (.*) index\.html$ /$1 [R=301,L]
The code above is causing a 301 / permanent redirect. It makes any page that has been moved or redirected not loose it's value.

I highly recommend that you do this asap and optimie your site and efforts.

** Remember to change 'yourdomain.com' to your actual domain name.