IE7 Beta 3 bug demo with changing CSS 'display' property in run-time (javascript)

Affected browsers:: 6.0 – 7.0b3, maybe earlier versions too

I cannot clearly classify this bug, but this is a minimal example of code which affects this bug. This bug happens in a specific combination of <fieldset> with relative positioned element, wrapping <div> with 'background-color' property and block which display property changes (none/block) in run-time via JavaScript.

Block with position “relative” stays on place when another block becomes to be visible via changing display property from 'none' to 'block' and vice versa.

Here is example:

Collapsing block, click on me to toggle

Fieldset

This block have relative position. The problem is here — this block does not shifts down when collapsing block expands.