htaccess www

First of all you need to turn the rewrite engine on

Options +FollowSymlinks
RewriteEngine on

Redirect www to non-www ... eg http://www.webarto.com > http://webarto.com

RewriteCond %{HTTP_HOST} ^www\.webarto\.com$ [NC]
RewriteRule ^(.*)$ http://webarto.com/$1 [L,R=301]

Redirect non-www to www ... eg http://webarto.com > http://www.webarto.com

RewriteCond %{HTTP_HOST} ^webarto.com [NC]
RewriteRule ^(.*)$ http://www.webarto.com/$1 [R=301,NC]