I think either it's not supported or I'm just too stupid. In this case I'd prefer the last one. I'm using Firebug to do my .css editing. Now I've got the problem that I've got to edit some pretty big css-files (few thousand lines of code). So I would like Firebug to display line numbers. Is that possible? If yes, how?
I also would have thought this was an easy one, but it appears not.
This is apparently open issue 2153 on the Firebug issue list, with a type of Enhancement, a status of Triaged, and no owner. I suggest you (and anyone else who wants this functionality) go star this issue to show that people care.
I'm not quite sure I understood the question fully. With what feature did you need line numbers?
When you inspect an element firebug splits into two panels. The right panel has 4 tabs: Style, Computed, Layout, and DOM. When selected, the Style tab will have the style information along with the document and the line number that it appears on positioned to the far right of that panel. Clicking on the file name or line number will pull open the CSS tab to show the style in the context of the css file.
I am not sure I understand your question, but
Firebug allows you to see the css file and the line of each css style in HTML -> Style.
See the current graphic on the Get Firebug landing page:
Line numbers are displayed under "Script" but if a user attempts to see line numbers under HTML they are not available.
My guess is that the line numbers are not necessary in the HTML view. Personally I don't use line numbers when using Firebug.