In any case, one bug that I successfully vanquished today involved the humble
<option> element. My HTML looked something like this:
<select name="categories" multiple="multiple" id="catfrom" size="20"> <option>entertainment</option> <option>movies</option> <option>sports</option> <option>news</option> </select>
I was having all kinds of strange problems in IE, which I finally tracked down to the following gotcha: in IE, the value property of an Option object is empty if the corresponding option tag doesn’t have a value attribute. This is counter-intuitive because in HTML if an option attribute is omitted the text inside the option element is used as the value instead. Mozilla browsers duplicate this in their handling of the Option object; IE doesn’t. Hopefully this tip will save someone some debugging time in the future.
Update: David Lindquist pointed me to Microsoft’s free Script Debugger.