How do you test the web applications (both server side and client side code)? The testing method has to work irrespective of the framework used (struts, spring web mvc) etc.

I am using Java for the server side code, Javascript and HTML for the client side code.

This is the sample test case of what I am talking about:

 1. When you click on a link, the pop up opens.
 2. Change some value in the pop up (say a drop down value) and it gets saved 
    in the DB.
 3. Click the popup again, you get the changed values.

Can we simulate this kind of thing using unit test cases? Is JUnit enough for this?