Web Applications: J2ee Or Javascript/css/html

I'm currently programming web applications using AJAX/CSS/HTML and they're pretty cross-browser. However when I heard of this language J2EE I had second thoughts. But I ran into GWT (Google Web Toolkit) which compiles Java code to Javascript/HTML. With this said, my mind tells me that Java developers desire to use Javascript/HTML languages to create web applications over Java.

So, which one should I start developing web applications in? Java? or Javascript

Well, I would say it depends, and it could even be both (easy answer)...
In creating a web application which is not only a bunch of static files, you will always have two parts where your code will run :
- on the browser (in Javascript typically)
- on the server (in J2EE, PHP, CGI, whatever)

I am currently on a project using AJAX philosophy on the browser, with ext-js Javascript framework notably. This is to increase user experience : no more page loading, dynamic,independent panels in different parts of the page, immediate data validation, etc. However at some point, these Ajax call do call some URL on the server, for it to actually do something (that is their reason in life). For the server part, I use the Web part of J2EE, namely, a Tomcat server with WebWork as controller, JSP pages for HTML views, and JSON for data exchange with browser.

I would say it is quite common to use both J2EE and AJAX, as the requirements are independent :
- you will want AJAX if you want a sexy 'Web 2.0' UI, instead of a awful succession of pages which reload entirely each time
- you will want J2EE if you have some complex business logic (maybe not if you only need to put and retieve data in a DB without any processing), or some complex integration with other server systems (using JMS, or connection pooling, etc).