How to redirect site.com to www.site.com?

[SystemOAD]

This is the code I have always used in my htaccess files:

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

Keep it at the top as you where told (with the change of that second line) and it should work fine mate.

Also check that your host accepts the use of htaccess files as some do NOT allow them to be used. In which case you need to ask your host to allow the use of htaccess.