A lot of developers don’t like having their sites loaded into a frame with Digg’s new DiggBar, inspiring several scripts to get rid of the bar. John Gruber came up with a short PHP script that prevents the page from loading with a nasty message if it detects that it’s being loaded in DiggBar’s frame. Gruber’s script inspired Phil Nelson’s WordPress plugin, which adds that script to any WordPress site.
This is very similar to a standard frame killer, except it only affects the Digg bar while letting other frames load your page.
To install it, unzip the archive, drop ‘undigg.php’ in /wp-content/plugins, and enable it in the plugins screen.