How to automatically detect bugs in a web application?

I have a web application in Vaadin. It has got some forms, search fields, buttons, etc and supported by a SQL database. I have been using Selenium, Sahi Open Source and some other tools for automated GUI testing.

Problem is: With recording GUI actions for automated testing isn't really useful because it seems more manual work than automated because I need to record the tests manually anyway.

Question is: Is there any better way to test a Web Application? How do you test your web application? Is there any free tool which automatically detects bugs in my web application?