It's recommented to install addon Color Toggle or Blank Your Monitor + Easy Reading, thus when some web pages goes ugly, you can revert to firefox defaults easily.
For Chrome, try Change Colors
fg: #000000
bg: #ffffff
link: #0000ee
visited link: #551a8b
fg:#eeeeec
bg:#2e3436
link:#edd400
visited link:#8ae234
[2011-09-12 21:32:42]
fg:#eeeeec
bg:#2e3436
link:#729fcf
visited link:#ad7fa8
[2011-09-15 12:59:17]