I do it all the time, but there's no need to have that function built directly inside the browser. There are all-purpose capturers out there, and I'm very happy with the Faststone Capturer (FSCapture, not the image viewer). Meanwhile it's shareware, but the last freeware version can still be found on the web, e.g. here
www.chip.de/downloads/FastStone-Capture-Letzte-Freeware-Version_20749866.html
Actually I've made a macro long ago, that creates a button and a little menu for it in K-Meleon:
http://kmeleonbrowser.org/forum/read.php?9,100997
But you can just as well use FSCapture as a standalone tool, and that's what I do myself. The macro merely adds the button and menu, which then call the tool.