parsing HTML text

I have written form screen which has as one of it's elements a <textarea> box in which a user can input some text --like a simple bio-- which will appear on another screen. I'd like to edit check this text. It would be a good idea to make sure that it has, among other things, no <form> elements, say, or to make sure that if a <font> tag occurs, that a matching </font> tag is present. Is anyone aware of a class or a package which I can use to parse this text and do this kind of validation? tia -lee -- When the birdcage is open, | donate to causes I care about: the selfish bird flies away, | http://svcs.affero.net/rm.php?r=leed_25 but the virtuous one stays. |