I've checked the privacy settings and couldn't see any way I could go invisible on Facebook as I'm getting fed up with random people popping up to chat when I'm busy. I didn't post it there as didn't want to offend anyone who thought I may be referring to them, but can you go invisible the same way as on IMs?
There is a thing (bottom right hand corner) where you can go 'off line' (can't find it at the moment as I am on an iPad and it doesn't allow you to 'chat').
There is a thing (bottom right hand corner) where you can go 'off line' (can't find it at the moment as I am on an iPad and it doesn't allow you to 'chat').