Configure Firefox

Comments:

Go to URL about:config and set the following:

key	value	comment
image.animation_mode	once or none	Play GIF animations once or never. (Makes web ads far less irritating.)
security.warn_entering_secure security.warn_entering_weak security.warn_leaving_secure security.warn_submit_insecure security.warn_viewing_mixed	false	Eliminate unnecessary pop-up warnings about SSL.
browser.chrome.toolbar_tips	false	Eliminate pop-up tooltips. I find them to be irritating and generally useless.
browser.enable_automatic_image_resizing	false	Screenshots often become illegible after resizing.

To get rid of the annoying little arrow things on the "Back" and "Forward" buttons, add the following line to userChrome.css:

.toolbarbutton-menubutton-dropmarker {display: none}

On Mozilla 1.5 on Windows XP, to make it look more like the old-fashioned Windows GUI theme, the following addition to userChrome.css was necessary (no idea if it's still applicable, but I'm writing it down just in case):

menupopup, popup {
  border-width: 1px !important;
  -moz-border-top-colors: ThreeDShadow !important;
  -moz-border-right-colors: ThreeDShadow !important;
  -moz-border-bottom-colors: ThreeDShadow !important;
  -moz-border-left-colors: ThreeDShadow !important;
  padding: 2px !important;
}

menubar > menu[_moz-menuactive="true"] {
  border: 1px solid transparent !important;
  background-color: Highlight !important;
  color: HighlightText !important;
}

2007-06-02
resizing added 2007-07-11
comments cleaned up 2007-08-10
added userChrome.css and old Mozilla stuff on 2008-04-06.