Automated webapplication testing

There exists a lot of ways to test a web application but which one is the most effective way, which reduces time effort and increases productivity.
1 answer

Use selenium

If the domain of the web application is big enough, it make sense to test the web-application automatically e.g. you can use selenium.
Firefox Plugin: Easy to install, selenium is available as Firefox plugin
Easy to use: Record your test-cases and play the recorded user interactions again
Export to Java: The recorded test-case can be exported to java for using it in a junit test case.