This page is mainly dealing with customization issues.
Before customizing Mozilla you should look read a few pages with tips regarding Mozilla:
I changed some parts of my Mozilla, especially by installing my favorite theme called Skypilot. I now don't have any extensions installed by default, the ones I used previously either slowed down the browser noticeably and created problems or were just unused most of the time. I have "fixed" some preferences by adding them to my user.js:
You could also use e.g. user_pref("browser.bookmarks.file", "D:\\some\\path\\bookmark.html") to have your bookmarks somewhere else. My userContent.css looks like this:
I finally found something useful to do with the userChrome.css. I now use it to hide several menu options which are there twice or which I never use and always clicked on in the wrong moment:
If you see this text, then you are using an old browser. The information on these pages should be fully accessible. But this page uses Cascading Style Sheets which your browser does not interpret correctly. If you want this page to display styled use a current version of Netscape (recommended version 7.0 or higher), Mozilla (> 1.0), Opera (>6.0), or Internet Explorer (>5.5?).