html parsing for errors

I am writing a Servlet which takes input from an html form.  I want to be able to detect 3 things:

1) malformed href tags... missing quotation marks, etc

2) unclosed tags... a missing table tag could render the site unreadable

3) undesirable tags.  I would rather not allow users to blink their text or to use nasty font colors.

If someone knows of a public class that addresses this problem that would be great.  I'm willing to modify something that does 2/3 of the functionality.  The second requirement is the most critical.
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JodConnect With a Mentor Commented:
Look up:


which will parse html pages for you.

Also try:

JavaCC is a parser generator - you give it the language spec and it will generate the code for the parser for you (in Java). They have an HTML language spec ready to use but you can generate your own spec using JavaCC to match which tags you are interested in.

Finally, a ready made HTML parser is available at:

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