if you want to join domain and subdomain www, you should do the following:
1 open .htaccess in your root folder with any editor
2 wright at any place (at the end f.e.)
Options +FollowSymLinks
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.your_site\.ru$ [NC]
RewriteRule ^(.*)$ http://your_site.ru/$1 [R=301,L]