Besttoolbars Add-on Framework and ToolbarStudio allows you to create Add-ons and Toolbars for all major browsers:
Reduce your development time by writing one piece of code that works in all browsers.
Less time developers spent making your Add-on means that you pay less.
Write just one code snippet to make change to all browsers all at once.
Supports latest versions of all major browser. Moreover it will support all future versions of browsers.