To enable safari web inspector
Enable Web Inspector The Web Inspector allows you to easily see how the source code creates the web page. You can inspect various elements of the web page and view their style, metrics and properties. If you select an element in the inspector window, it will briefly be outlined in red on the web page. 
To enable the Web Inspector, open up Terminal (located in Applications/Utilities), type the following line and press return: defaults write com.apple.Safari WebKitDeveloperExtras -bool true
