Firefox at home and work. From a security perspective the only brower that you can properly handle cookies and block scripts with is firefox with the proper plug ins. From a developer perspective you really should do a browser check and make sure it works with at least IE6 and IE7. IE6 is still used by everyone in the corporate world still on Windows 2K, which is a very high number (unless they have Firefox but a lot of group policies block its installation). IE8 has IE7 computability mode so you can publish the site while you work on making it work properly with IE8. As much as I hate IE it will be the brower most people visiting a published site will use.