Building on yesterday’s list, I’ve found (through reader recommendations) six more web developer extensions that have been updated for Firefox 1.5. The caveat, however, is that I’ve only personally tested one of them (ColorZilla). Descriptions below are taken more-or-less directly from the extensions’ pages.

ColorZilla
Advanced Eyedropper, ColorPicker, Page Zoomer and other colorful goodies. With ColorZilla you can get a color reading from any point in your browser, quickly adjust this color and paste it into another program. You can Zoom the page you are viewing and measure distances between any two points on the page. The built-in palette browser allows choosing colors from pre-defined color sets and saving the most used colors in custom palettes. DOM spying features allow getting various information about DOM elements quickly and easily. And there’s more…

Console²
Console² lets you display errors filtered by type (Errors, Warnings, Messages), language (JavaScript, CSS, XML) and context (Chrome, Content). Furthermore it provides a simple search box (as seen in the History and Bookmarks sidebars) and some accessibility improvements.

IETab
This extension embeds Internet Explorer in tabs of Mozilla/Firefox, letting you see how a page is displayed in IE with a single click.

LiveHTTPHeaders
This extension makes information about HTTP headers available in three ways: by adding a “Headers” tab in the “View Page Info” dialog; by adding an item to the “Tools > Web Development” menu that displays HTTP headers in real time; and by allowing you to request headers and “replay” a URL (beta functionality).

User Agent Switcher
Adds a menu and a toolbar button to switch the user agent of the browser.

Quick Locale Switcher
Quickly change and apply a different general.useragent.locale preference from the tools menu.