Did you know that the z-index property in the CSS specification is at best vague and at worst frustratingly broken? That chrome will sometimes interpret positive integer z-index values as auto while firefox will interpret those same values as integers? That firefox will be fine with nesting a mix of absolute and fixed positioned elements but chrome will choke? Well it is, they do, and they will.
And all three of them can go screw themselves and take a long route with a short TTL.