A bug report for maphilight lead to me becoming aware of a fascinating quirk in IE. A quirk in which IE holds to published standards with fanatical zeal, contrary to everything one might have come to expect, and far in excess of Firefox/Opera/Safari.

When you use the .innerHTML property to add an element to the DOM, IE will fire an “unknown runtime error” if that element is incorrectly nested. So trying to place a <div> inside a <p> (as was the case in the bug report) will error very unhelpfully.

Surprising behavior.

Anyway, this led to the release of maphilight 1.1.1. (Which also includes an official minified version of the file, for convenience’s sake.)