Sometimes, removing positioning from an element after layout fails to update properly. In the attached test case, the red box inside the yellow one is initially positioned but the positioning is removed. However it does not reset to its normal position until you resize the window.
Created attachment 6277 [details]
I'm going to attach a patch.
Created attachment 6289 [details]
Comment on attachment 6289 [details]
Darin landed this in r12682.
This is a Quirksmode bug:
Element retains position: absolute after class change
Reported on 3 October 2006
Test page: http://indorgs.virginia.edu/betech/bugs/safari-stickyposition.html