Many of us use browsers very often, and maybe some of you just don't like the default white color of many web pages. I don't like either.
I am used to work and view documents in black background with white fonts color, just like the appearance of command line terminals. So I began to search the method which can help me in reversing my browser's foreground and background colors.
The answer for Firefox is Color toggle by Nathan Baker. Color toggle is a simple plugin which is very easy to use for swapping or toggling colors between two color profiles. Therefore with this plugin, you can toggle your foreground and background colors in very quick key pressing (the default is Ctrl+Shift+u).
The original looking: