When a user enters a date, it is underlined in red (because it is not in the dictionary somewhere). This is certainly a problem in FF, possibly in most browsers. Is there a way to mark the input field as "don't expect English words here?"
Use the spellcheck attribute. Tested in Firefox 3.0:
spellcheck
<html><body> <textarea>Teh speling is checkd.</textarea> <textarea spellcheck='false'>Teh speling is not checkd.</textarea> </body></html>