Firefox’s interface is cleverly designed using JavaScript and XUL, and using what’s referred to as chrome URL’s you can actually open specific windows in a tab or the sidebar. This includes things like the management windows for bookmarks, saved passwords, downloads, extensions, and more. They can even be bookmarked for quick one-click access to them in the future.
Below we’ve got our top 5 chrome URL’s that can be used in Firefox 3, and all you have to do is copy the URL into the address bar to see what each of them do. Don’t forget to bookmark the ones that you’ll use frequently, and here are some instructions if you want them to open in the sidebar.
Note: The URL’s will obviously only work in Firefox.
1) Bookmarks Management
Used for: Managing bookmarks, tags, and history.
URL: chrome://browser/content/places/places.xul

2) Downloads
Used for: Managing past and active downloads.
URL: chrome://mozapps/content/downloads/downloads.xul

3) Extensions
Used for: Enabling, disabling, and uninstalling extensions, themes, and plugins.
URL: chrome://mozapps/content/extensions/extensions.xul

4) Saved Passwords
Used for: Managing passwords stored by Firefox.
URL: chrome://passwordmgr/content/passwordManager.xul

5) Preferences
Used for: Configuring different options in the browser.
URL: chrome://browser/content/preferences/preferences.xul

Runner Up: Browser inside a Browser
Used for: Displaying a browser inside a browser. This is more for fun than anything else.
URL: chrome://browser/content/browser.xul

[via Firefox Facts]

Nice, you can also add chrome://global/content/config.xul to the side bar
Greetings
That’s pretty cool, I think the bookmark management one would be really useful.
This is something that the Mozilla team should implement by default in Firefox, like Opera do
I’ve done the add-ons one for a while no problem. I tried adding the Preferences one and while it works, it un-maximizes Firefox when I click on it.
I saw that one but I figured it wasn’t anything too great since you can easily type about:config into the address bar to reach that page. Putting that in the sidebar would make it a little cramped, too.
Yeah, that’s my favorite one as well. It’s nice having it open in such a large area.
I noticed that, too. I was surprised that it was able to resize the window since I have the JavaScript option disabled for letting code resize my window. It’s still nice if you want the Applications tab to utilize more of your screen, or something along those lines.
Actually, my favorite one is the browser-within-a-browser! It allows you to have what are basically sub-tabs!