Edit2: Sorry, I messed up this whole question. I am centering an ul, and it'll be slightly off to the right. If I do the same exact thing using divs, it'll center correctly.
Here I use div: http://cssdeck.com/labs/rt6p03qe Here I use ul: http://cssdeck.com/labs/g4iyhnqb
As you can see, they are slightly offset, even though the code is the same for both.