The Rest of the Develop Menu
Now that you know all the features of the Web Inspector, the remaining items in the Develop menu are self-explanatory. You can enable and disable JavaScript debugging or profiling from the Develop menu.
The last six items in the Develop menu let you configure how Safari behaves. You can disable caching, image downloading, CSS stylesheet rendering, JavaScript execution, the runaway JavaScript timer, which keeps an eye out for JavaScript code that never finishes running, and you can disable site-specific hacks, which are hacks added by Apple for specific kinds of problems that have been encountered.