[chrishajer]

Add this to the header.php in your template:

<link rel="shortcut icon" href="<?php bb_option('uri'); ?>favicon.ico" type="image/vnd.microsoft.icon" />

Then, make sure you have a favicon.ico in your forum’s root directory. You could also put the favicon in another directory (like the website root folder) and reference it there like this <link rel="shortcut icon" href="/favicon.ico" type="image/vnd.microsoft.icon" /> instead.

http://en.wikipedia.org/wiki/Favicon