There are a number of tools available, both open-source and commercial which get lumped into the bucket of ‘functional testing tools’. Essentially they help you, well, test the functionality of your application.
One of these tools for testing web-based applications is Selenium. Selenium has at its core three different components: a record/playback tool (Se-IDE), language bindings (Se-RC) and a distributed execution framework (Se-Grid).
I put up a post on my blog called The Selenium Value Chain which briefly discusses each and the progression between them. For teams working on web-based projects, Se might be a strategy you employ to help build a regression suite for your new (or the existing) features.