Redirect without WWW 

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



Redirect with WWW 

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