You’ve probably read(and experienced) a lot on how Google penalizes websites/blogs for duplicate content.
Whats that? You say your content is 100% unique and home-made? Well, thats not the utter and complete truth, because google indexes your content from http://yoursite.com and http://www.yoursite.com, effectively crawling your blog/website twice. This also dilutes the effectiveness or incoming links as some may point to the www version and others to the non-www version of your website.
Now you might think that the Googlebot isnt so dumb, and it isnt, but all the same its best to fix the problem.
Thats where the enforce www plugin comes in. From the page:
This plugin will help preserve your permalinks by enforcing your no-www or yes-www preference (http://example.com/ vs. http://www.example.com/) and will strip off index.php from the ends of URLs.
Once you’ve installed the plugin, set up your preference for your domain from Options->General tab on your Wordpress admin menu, and thats all there is.
I use the non-www preference for Shypy.com, so even though you type in www.shypy.com in your browser, it always takes you to http://shypy.com (no WWW!) 
