Firefox and the "about:config" file
First, for those that do not already know about it Firefox allows users to change many preferences in the about:config file. To access the file just type "about:config" without the parenthesis, into your location bar.
You will notice on the config page a filter at the top. To use the filter type in any word, such as tabs, that relates to a preference name and the page will update to show all preferences with that word in the title.
There are 4 columns on the config page. Column one is pretty self explanatory, it contains the "Preference Name". Column 2 is the "Status" this shows whether the preference is still set to the default or if it has been changed (hint: if you change a pref from the default value that entire line shows in bold text allowing you to know at a glance if you have changed it or not). Column 3 is the "Type" this refers to the type of preference it is, there are 3 types. Boolean, integer and string. Boolean simply means true or false and by double clicking that preference you will change it to false if it was true or true if it was false. Integer simply means you are dealing with a number value and changing the number will change that preference. String values are letters, words, URLs or anything dealing with non-numeric characters. Column 4 is the "Value" basically what the preference is set to do or show.
Now that we know a little about the "About:Config" I will give you a couple of my favorite changes that I make to my Firefox.
First, I generally set browser.enable_automatic_image_resizing to false. The default is true and so when a picture appears on a page alone it is shrunk down so you can see the entire image without scrolling. I would rather start with a full sized picture on a page so I know what I am dealing with.
Next is the browser.tabs.closebuttons. This one is an integer and with this you have 3 options. 0 which means only your current tab will have a close button, 1, the default, which means all your tabs will have a close button and my favorite which is 2 and that means no tab has close buttons.
Finally is the privacy.popups.showBrowserMessage which is another boolean type. The default on this is "true" which means you get the little window in the top of the tab that tells you when a popup was blocked. I set this to false as I don't really feel I need to know when one has been blocked.
There are many other preferences that can be changed in the Firefox config file and by now you should have a basic understanding of how to change them yourselves. Though here at the end I will caution you to only change one preference at a time, especially if you are unsure what it will do, so you can go back and fix it if the change has an undesirable effect.