Interesting. According to HTML 4.01, it must be greater than zero:
http://www.w3.org/TR/html401/present/fr ... edef-FRAMEHowever, is there a problem with real-world browsers and a zero value? Should
CSE HTML Validator "complain" about marginwidth or marginheight being 0 as a "real-world" issue? I am not aware of this being a real-world issue, but if it is, then please let me know and I can address it.