div not centering with margin: auto?

Question

I've got one fixed div that's 100% screen width, and another one inside it that's set to a width in pixels. For some reason, even though it has width: auto, it's aligning left:

http://jsfiddle.net/jv87N

I can't think of any reason that the margin: 0px auto; wouldn't work.

Answer 1

Remove fixed position from #nav.

margin:0 auto does not work with absolute/fixed position.

Updated fiddle here.