One of the most useless feature in Facebook is the chat or Instant Messenger. Here is a simple hack which will let you remove for good.
From our Firefox add-on collection, you should already have adblock installed.
Login your Facebook account.
Click the little red Ad-block icon and select Preferences.
Click the filter menu, select add filter.
In the New filter blank field, paste this code:
facebook.com#div(id*=presence)
Click APPLY, then OK. Have a quick page refresh (F5)
Done, the Chat box and the toolbar have disappeared forever from Facebook! This however has left the script running. If someone can figure out which of the million random scripts is running to achieve chat, please let us know, so we can add this to ad-block