What does WTF stand for?

Wtf traditionally means "What the F**l{". But in Facebook, it usually means "Welcome to Facebook".

Joke about "WTF" on Facebook".

One day a boy posts "WTF!?" on his wall.

Next day, his dad reads it, and asks his son what it means. His son goes "Uh... It means Welcome to Facebook.".

So, a few weeks later, the dad's boss joins Facebook.

The dad writes "Wtf!" on his boss' wall.

Next day he gets fired. Poor Guy.