Firefox 1.5 RC2, Internet Explorer 6 and 7 cut off the drop-down menu option, if the user scrolls far enough along to the right.
Other Browser Behaviour Noticed
Firefox 1.5 RC2 adds a line of space below the form, due to a fixed default height for the div. Setting zero padding and margins to everything doesn't remove this. Only giving a specific height to the div works.
Opera 8.5 and 9.0 Preview 1 don't show a tooltip for the option, which has a title attribute ("option").
Internet Explorer 6 shows no tooltips at all, on either the select or the option.
Internet Explorer 7 shows tooltips on the select and option elements.