Add following in .htaccess file following:
Options +FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} .
RewriteCond %{HTTP_HOST} !^yourdomain\.com
RewriteRule (.*) http://yourdomain.com/$1 [R=301,L]
Replace [yourdomain] and [com] to your real domain and extension in line 5 and 6.
What's the advantage of merging those two URLs?
It's good for pagerank !!! (It will not split visitors.)
