Last month, Avinash Kaushik (a web analytics guru) posted an article about the importance of qualitative web analytics. In it, he stresses the importance of identifying why your website behaves the way it does. While tools like Google Analytics might be able to tell you what happened on your website - pages per visit, bounce rate, conversion paths - it's nearly impossible to use them to answer why.
Asking why takes things a step further. Once you figure out why visitors are leaving your homepage (or your checkout page, or any other page for that matter), you can implement (or even better, test) fixes to stop the bleeding, reduce bounce rates, and increase conversions. Avinash suggests performing heuristic evaluations, like the one available from Dr. Pete. A heuristic evaluation (in this case, a checklist) is a quick way to see if your website adheres to an established set of best practices (for example - is your font size and spacing easy to read?).
Other methods addressing "why?" include usability tests (in-person or remote, like UserTesting.com), surveys, and of course, Concept Feedback. Concept Feedback is a quick way to get qualitative website feedback, and generate new ideas that help answer the why question.
If you have other tools or techniques for answering "why?" on your website, please let us know in the comments!