1.When the user log off from the system he /she can able to access the application using browser�s beck button or using early stored url (pls tell me non java script solution )
There are two things that must be in place to prevent this:
1. Every single interaction with the server must check for a valid user. One way to do this is to write a Servlet filter that does the check. If you're using Struts, another way is to write a single base Action class that all your other Action classes extend and put the logic that checks for the user in this base class.
2. You must tell the browser not to cache your pages. Again, if you're using Struts, the following entry in your struts-config.xml file will accomplish this:
2.what is the best an easy web application development tools and frame works in java
The best framework would of course be Struts ... what a silly question You may also want to look into Java Server Faces (JSF) and Spring. If you're ready to jump on the AJAX bandwagon, there's a really good framework called DWR that's worth looking at.
There are lots of good development tools out there. The free Eclipse framework with the almost-free MyEclipse ranks high on my list. NetBeans has some good tools as well. If you or the company you work for are willing to spend some money on development tools, IBM's Rational Application Developer and IntelliJ's IDEA are both exceptionally good.
3.what are the method to improve the web application performances obstacles
This is way too broad a topic to cover here. Just Google "j2ee performance tuning" and you'll get a lot of good reading.
The Struts development team must have liked the framework WebWorks since the Struts Action Framework 2.0 will be based on WebWorks. If I was starting a project from scratch and did not already have a team of experienced Struts developers, I would likely not pick Struts. But then again, I don't know what I would pick over Struts. A major project at my company picked Tapestry and a lot of people seem excited about Ruby on Rails.