How can I redirect incorrect hostnames to the proper one?

Sometimes people access your site using a different hostname than you'd prefer.  This example shows how to redirect a person who mistypes your site (wwww instead of www) to the proper URL.  This assumes your DNS has that entry, which isn't a bad idea.

This uses mod_rewrite in the .htaccess file:

RewriteCond % ^wwww\.(.+)
RewriteRule ^.* http://www.%1 [R=permanent,L]