3D differential geometry

I'm going to present something about 3D GR in some days.  However, I keep reading that 3D is conformally flat, but I don't see why.  Wikipedia says that the Weyl tensor vanishes, but that's apparently not enough for 3D.  What is the significance of (what wikipedia calls) the cotton tensor, and why does it also have to be 0?

I should probably go read some more papers, but if any of you guys have some insight, that'd be nice.

Could you phrase that in the form of a Calculus I problem?

>>2
Could you rephrase that using proper English?

>>3
Could you restate that using your lips on my anus?

>>4
MmmMppHH bblbbphsbl fupppLEFUP mmmph blhhhhhfarP!

>>5
OOOOHHHH,  I get it now!

The answer is 4.

I hate you guys

>>6

That shit has never been funny. Please stop.

>>7

:<

>>7

<hugs>

All that matters is you slip it in somewhere that 0.999... = 1. Everyone will leave your talk with their minds blown.