This is the infamous Big Blue Ban Button, or 'BBBB', or '4B', as it is oftentimes referred to around NFSunlimited. Well, okay, it's not the REAL BBBB, rather a picture of it, let's be perfectly clear about that. I mean, if you click *this* BBBB, absolutely NOTHING is going to happen. I'm pretty sure of that anyways, so don't bother trying. Really.
The Big Blue Ban Button is used by the Forum Police in their favourite pastime - banning noobs who break the Forum Rules. Let it be made clear at this point that (despite the obvious contradiction to the pervious sentence) the Forum Police don't necessarily relish the idea of using the 4B. However, as can be seen by its extremely worn-out and battered state, it does get used rather regularly.