Apple’s latest builds of WebKit (which is really just Safari to most Mac users) includes an incredible, dashboard-style inspector palette that lets you examine parts of a web page’s structure. This is incredibly helpful for developers and it looks great too.
You can grab it from here and follow the simple instructions. You just need to download the WebKit application and run a single command in Terminal. Then, once you launch the WebKit application, simply right-click/control-click on a part of the page and you’ll see the inspector.
I would love to see this idea expanded upon, it’s a real treat for web developers. Maybe someday we’ll see this sort of feature make its way into iWeb too.