Version 1.1 of the Web Developer extension for Firefox is now available with some new bells and whistles. If you already have it installed, just check for updates in the add-on window. Otherwise, it can be installed from the chrispederick.com blog.

you can now ‘Edit CSS’ and ‘Edit HTML’ on the same page at the same time.

On a related note, don’t forget that IE7 also has a Developer’s Toolbar. It’s not as good as the Firefox version, but when the web design problem you looking for is only visible on IE, it works. (Isn’t it always?) To install, open the tools menu in IE7, and choose Manage Add-ons, then Find More Add-ons. It’s in the developer tools section.