Better anti-aliasing on iPad when using position: fixed, why?

Question

I noticed that when using position: fixed on an element, the text on the iPad (iOS 5.0.1) is being rendered better than without position: fixed. This is especially the case for white text on darker background.

My question is how to make use of this improved anti-aliasing without using workarounds such as position: fixed.

Below you can find an example picture and the corresponding code.

http://jsfiddle.net/t4kTm/

Answer 1

I don't know why that is, but I do know how to control anti aliasing in webkit browsers:

-webkit-font-smoothing: none; /* Obvious */
-webkit-font-smoothing: subpixel-antialiased; /* This is what quite a few browers already do*/
-webkit-font-smoothing: antialiased; /* Even more than the one above */

Will this help?

Answer 2

After updating to iOS 5 I wasn't able to reproduce this anymore - weird.