Within the Firefox DevTools you have similar options to edit the HTML. You can edit attributes and text contents (and even tag names, which was not possible in Firebug) by double-clicking them. To edit the whole HTML structure under a specific element, right-click the element and choose
Edit As HTML from the context menu. The only thing that's not yet working is the live update of the website while typing, which is reported as
bug 1067318 and
bug 815464.
Note that I have written a
migration guide explaining the most common questions for Firebug users. Please let me know if you're missing something there. Furthermore, there is a
bug report covering all Firebug features that are currently missing in the DevTools. If you're missing something that's not yet filed blocking that one (see the list under "Depends on"), please file it and mark it as blocking bug 991806.
Last but not least, I want to note that while the DevTools are still missing some (important) features of Firebug and their UI is not as good as Firebug's, they are in some areas already far more powerful than Firebug. E.g. they have an
Animations Editor, they allow you to
filter the CSS properties, they have a
color picker and different other
CSS property helpers, and they allow to
inspect the fonts used within an element, to name just a few of their features.
Sebastian