If you have a website and want to force www.domain.com Use the following .htaccess code
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
If you want to eliminate the www prefix like domain.com then use the following .htaccess code
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.(.+)$
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
