How do I disable my mouse's "back" button for a single Firefox tab?

How do I disable my mouse's "back" button for a single Firefox tab?

Sometimes, accidentally hitting my back button can be a huge pain. For instance, on Mibbit.com, if I hit that button I will have to re-logon to IRC. Probably the easiest choice would be a Firefox extension so I can just click a button to clear the history for the current tab, but I haven't seen anything like this.