FAQ: Please read these Frequently Asked Questions before posting.
1. What are the basics of userChromeJS?
Please see the README.txt file.
2. Why doesn't a script change take effect on restart?
3. Overlays don't seem to overlay, what can be done?
userChrome.loadOverlayDelayIncr = 2000;
NOTE: It's better to use either the multiple import files method OR all .xul files in a folder method and not mix/match.
4. How about a nice repository and collection of scripts/overlays, like Stylish or Greasemonkey?
Yes, it sure would be nice if someone built that.