JavaScript to do it directly at the source or post the info in a submit to a servlet and let the servlet mail it using JavaMail. Here is something to get you started on the servlet side:

http://java.sun.com/j2ee/1.4/docs/tutorial/doc/

And, no I am not going to give you the complete code for a servlet to do what you want. Read through the tutorial and learn a litlle more about j2ee programming.

I would also suggest you learn more about html and the other technologies used in web programming (at least some of the basics) before you attempt to go much further.

If you wish to know how to do it in JavaScript, then find a JavaScript forum and ask again (or better yet, find a JavaScript Tutorial/Learning site and learn how to use it).

and no, you won't be able to send an email using the server entered by the user of the page.
Any mailserver worth anything at all will block any attempt by anyone who's not on the same domain (and/or has proper credentials) to send anything.

And no, I'm not going to help you do that in a JSP for the simple reason you shouldn't.
Use a servlet.