If you mean the possibility to directly debug JSP's, this feature is not available yet, but it is planned for the next version of IDEA.

Currently it is possible to debug servlets, generated from your JSP's.

In order to do that, start your Tomcat, and then connet to it from IDEA, using the Remote Debug settings. Make sure that the sources to be debugged are added to your Sourcepath, so that you can set breakpoints and perform different debug operations.