Q. Why cannot I see my modification on my JSP even I do a refresh? Is that a tomcat problem?

A: No, it is not tomcat, but your IE or your proxy server.
It will happen quite often. Every developer experiences the same.
If you are only developing and display on your local machine, it is easy. The followings would be I do in that order.

1.Refresh, of course
2.Go to IE explorer properties dialog, delete all offline files, your problem is solved.

If you upload your code on a server, then access the website, then you need to play cat and mouse games with them. Try let the proxy server know your page need to be updated. Do the same 2 items as on your local machine, if it does not work, the do the followings:

1.Temporally rename your page to something else, and access the "new" page.
2.Shutdown my website for a minute, and access it, the proxy will give me 404. Then restart.

Other people might have some more creative way, let me know!!!