There is a lot of confusion about tooltips on DropDownLists. Here's the facts.
IE for Windows does not support the Tooltip property or even the title attribute on the <select> control. This is because they create a separate window for the <select> tag that is above the rest of the info on the browser window. (Think of it as another layer.) The tooltip engine is actually on the main window layer, so the tooltip would appear behind the <select> element if it was to appear. This layered behavior also breaks popups that position over <select> tags because they are always on the main window layer!
The title= attribute is fully supported in the W3C specification, which is used by the DOM-based browsers like Mozilla, FireFox, Netscape, and Safari. So by assigning myDropDownList.Attributes.Add("title", "text"), you will get a tooltip on those browsers!
Finally, the suggestion to enclose the DropDownList in the
with a title= attribute will only work so long as the user does not point to the <select> element itself because of the layering problem.
We can only hope Microsoft puts <select> tags into the same layer in a future version of IE...
Credit goes to PLBlum