posted 21 years ago
This is what MSDN (that means it is true for latest IE) about SELECT element:
"This element is a windowed control and does not support the z-index attribute or zIndex property."
This also means, that SELECT object will appear on top of any "DIV" or "SPAN", with no respect to theirs z-index.
The only element so far, that is able to cover SELECT in IE5.5+ is IFRAME.
So, one possible sollution is to change your menu to put DIV's and/or SPAN's into IFRAME, and size that IFRAME to fit menu.
Another one, works with IE4, i beleave, is to "hide" selects (using visibility="hidden"), when you open menu over it.
Third, and the most popular one, is to design your pages, so that, menu will never appear on top of SELECT.
Forth, and this is the one that I am using (well, it works only with IE5.5+ and NS6.2+ , but my company is fine with it), is to write your own SELECT element using DIV tag (visit my website in a couple days - I am going to put an example there. It also support expand/collapse for optgroups, and a lot more).
Fifth is to ignore this issue and wait that next IE version will have it fixed. (Call it "third party tool issue").