On Firebug, when you hover the layout section, the respective section of the selected HTML element is highlighted. I use _a lot_ this feature, it is very useful

On Firebug, when you hover the layout section, the respective section of the selected HTML element is highlighted. I use _a lot_ this feature, it is very useful, and IMHO is a must-have for a webdev tool :-) Another feature I would like to see is a 'Disable cache', and a 'Open source code in a new tab' (the things I use more of Web Developer Tools :-) )