You can do a lot with Firefox that a lot of people don't know about. Here's a video showing my Firefox setup.
I use both the VimFX add on for vim shortcuts and Stylish to easily modify the CSS of different websites, and Firefox's skin and theme itself.
You can also use Stylish with Google Chrome (if you don't mind CCing everything directly to the NSA), but I don't believe you can modify the actual browser tabs/url bar etc., only websites. Not sure about Chromium ATM.
My Firefox CSS: http://lukesmith.xyz/longterm/lukeskin.css
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See my website: http://lukesmith.xyz