What is the shortcut for inspecting elements in Firefox

It seems that Ctrl+Shift+C always open the inspector in "choose element with mouse" mode. [Linux, FF 26.0. Also works in Chrome.]

It's not exactly the same flow as context menu -> inspect element but I find it more useful. The hover tooltip sometimes gives me all the info I need. And it's more reliable — just opening the context menu generates a mouse event while Ctrl+Shift+C doesn't. E.g. with CodeMirror which plays games with invisible elements, using context menu usually lands me in the hidden textarea or fake cursor, while "choose with mouse" mode reliably gives me the styled editor content I wanted to inspect.

Windows: Ctrl+Shift+C.

Mac: Cmd+Option+C.

Ctr + Shift + C and function F12 button is default inspect element button for every browser. So if firebug isn't installed in your firefox then F12 button is the shortest shortcut for your goal.

I'm not sure about the way you do it in Mac OS, but on windows, if you select the element by pressing tab until you reach it, if you press the context menu key and then Q, you open the inspector on that specific element, like it happens when you right click on it.

I believe the context menu key is not a mac thing, but it seems that there are people that worked around to do it. See this question: How do I open the context menu from a Mac keyboard?.