chrome://global/content/alerts/alert.xulIt makes the Firefox window auto collapse and expand in the corner of your monitor screen.
2. Open Firefox inside Firefox.
chrome://browser/content/browser.xulThis opens another Firefox inside a tab in the the existing Firefox window.
3. Options inside a Tab
chrome://browser/content/preferences/preferences.xulThis opens the Options dialog box inside the Firefox tab. See the screenshot above.
4. Bookmarks Manager inside tab.
chrome://browser/content/bookmarks/bookmarksPanel.xulOpens the “BookMarks Manager” inside a tab in the Firefox window.
5. History inside
chrome://browser/content/history/history-panel.xulOpens the History Panel inside the Firefox tab.
6. See the Extensions in a tab.
chrome://mozapps/content/extensions/extensions.xul?type=extensionsOpens the Extensions window in the current tab.
7. Manage installed cookies in a tab window.
chrome://browser/content/preferences/cookies.xulThis opens the “cookies window” inside a tab.
8. Clear Private Data and History
chrome://browser/content/preferences/sanitize.xulOpens the “Clear Private Data” window inside the current tab.
9. Sliding Developers’ Credits
chrome://browser/content/credits.xhtmlA scrolling list of names of those who created the Best Web Browser for us
10. About Firefox in a tab.
chrome://browser/content/aboutDialog.xulOpens the “About Firefox” Dialog box inside the tab.
You can even install these addresses as bookmarklets in your browser so you can access them with a single click from bookmarks toolbar.
Add the tricks like these that you know in the comments.