Page 12: WordPress has no Way to Enforce URL Preference

Be default your wordpress blog can be accessed either by using http://www.site.com or http://site.com. Understand that to search engines those are different URL’s (one with a www. and one without). You can access your WordPress blog, and every single post, page, category, and tag with our without the “www.”. this means that every single page in your site has a duplicate – and you need to choose which one your’re going to use (and stick with it). I always use the www. version, and when I post in forums and comment on blogs I use the www. version too. The Enforce www. preference WordPress plugin will do just that, force your blog to always use (and redirect to) just one way or the other (which you set up in options). This is a very important plugin, because ultimately it will control how many pages you get listed in search engines, and rids you of problems with duplicate ones.