htaccess 001 redirects

So you figured out how to rename your htaccess.txt to .htaccess and your loving your SEF. Google is indexing your site, you have 20K pages listed on the search engines. But you decide to slightly change that SEF URL and BAMB

tons and tons of 404's

Or you don't like when people goto http://joomlamafia.com you want them to go to http://www.joomlamafia.com (go on click both links and watch what happens you cant go to http://joomlamafia.com without being redirected to http://www.joomlamafia.com can you?

You should really consider doing this because google among other bots will consider joomlamafia.com and www.joomlamafia.com 2 different websites because infact they are. This is how I do it. I also redirect any errors to the homepage to.

RewriteEngine On
RewriteBase /
Options +FollowSymLinks
ErrorDocument 404 http://www.joomlamafia.com
RewriteCond %{HTTP_HOST} ^joomlamafia\.com [NC]
RewriteRule ^(.*)$ http://www.joomlamafia.com/$1 [L,R=301]
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.shtml\ HTTP/
RewriteRule ^index\.html$ http://www.joomlamafia.com/ [R=301,L]