When using IE, you cannot put an absolutely positioned div over a select input element. That's because the select element is considered an ActiveX object and is on top of every HTML element in the page.
I already saw people hiding selects when opening a popup div, that leads to pretty bad user experience having controls disappearing.
FogBugz actually had a pretty smart solution (before v6) of turning every select into text boxes when a popup was displayed. This solved the bug and tricked the user eye but the behavior was not perfect.
Another solution is in FogBugz 6 where they no more use the select element and recoded it everywhere.
Last solution I currently use is messing up the IE rendering engine and force it to render the absolutely positioned div as an ActiveX element too, ensuring it can live over a select element. This is achieved by placing an invisible iframe inside the div and styling it with:
#MyDiv iframe
{
position: absolute;
z-index: -1;
filter: mask();
border: 0;
margin: 0;
padding: 0;
top: 0;
left: 0;
width: 9999px;
height: 9999px;
overflow: hidden;
}
Anyone has a even better solution than this one ?
EDIT: The purpose of this question is as much informative as it is a real question. I find the iframe trick to be a good solution but I am still looking for improvement like removing this ugly useless iframe tag that degrade accessibility.