Div with zindex=100 working fine under Firefox but not IE

[winstontuck]

HI

I have a div which I use as a popup datepicker. the style positions is
set to absolute and the zindex to 100. In firefox it behaves correctly
in that it stays the most top "form" and move over the <select multiple
in the background but in IE my selects displays over this div. The
normal text inputs goes behind. Why could this be?

Thanks