Majd Taby has some advanced tips for the WebKit inspector:
Google and the Chrome team have been pumping a ton of resources into the WebKit Inspector. The changes have enabled a whole new class of complex and ambitious applications that would have otherwise collapsed on their own weight. This is great news, of course, but as I talk to more and more web developers about their process and tooling, it became clear to me that many of them haven’t caught up with the changes or aren’t making effective use of the tooling available. This blog post attempts to remedy that, not only by walking you through the inspector’s feature set, but also highlighting certain techniques for bug hunting and feature development that I’ve found to be indispensable.