Do you use a  FaceBook Fan Page to promote your company, website or band? Have you tried visiting it with a mobile phone? There’s a bug in Facebook’s mobile browser detection and redirection logic that causes many Fan Pages to return a 404 “Not Found” error when visited with most mobile browsers. This bug doesn’t affect the iPhone, Android and WebOS browsers which are not redirected and get the desktop version of the fan page,  but S60 Webkit, Opera Mini, Mobile Internet Explorer, the BlackBerry browser and feature phone  browsers all see the 404 error.

I discovered this when I tried to open the page  for my BoostApps site using Opera Mini .   The issue is that by default Facebook Fan Pages have a fuggly URL like www.facebook.com/pages/BoostApps/175451287173. Not only is that a terrible URL for discovery and sharing but it breaks when visited with a phone browser.  Facebook’s mobile detection script redirects it to m.facebook.com/pages/BoostApps/175451287173 which is an invalid address.

Fortunately there is an easy fix, you just need to create a Username for you page.    Here’s how:

• Go to www.facebook.com/username/
• Log in if prompted
• Click the “Set a username for your Pages.” link
• Choose  your Page from the drop down and enter your desired username when prompted.

I choose “BoostApps” for my page’s Username. Now users can visit the page at an easy to remember URL: http://facebook.com/boostapps – and it works in both mobile and desktop browsers!

Facebook does require that your page have at least 25 fans in order to be able to set a username.  Usernames can only contain alphanumeric characters and periods. You can’t use a trademarked name that you don’t own. Choose your Username wisely as once it is set you can not change it or transfer it to a different page. For more information visit the  Usernames for Pages entry in Facebook’s Help section.