Here’s another cool tweak by adding a few things in your userChrome.css file. While it doesn’t really affect Firefox performance, it’s another tweak to make your Firefox browser, your own.

Here’s how to change the progress bar’s color:

• Open your userChrome.css (I recommend using ChromEdit Plus)
• Insert this code at the bottom /* Progress bar color */ .progress-bar { -moz-appearance: none !important; background-color: #XXXXXX !important; }

  NOTE: The six Xs should be replaced by a hex color value. If you aren’t familiar with hex colors, here are some web-safe colors.
• Save your userChrome.css
• Restart Firefox