Field verification?

I was wondering what (if anything) people are using to verify information in
a particular field. For example, say you wanted to make sure that the
Subject field was filled in before a ticket was closed. I searched the
archives and saw a response or two stating Javascript as an answer. Is it
possible to customize a scrip to halt the resolution of a ticket and pop up
a warning? What are do others do?

Feel free to send responses directly to me and I can summarize. Thanks.


Matthew Hanley