Top Firefox extensions for mobile content development

After putting up a poll about which Firefox extensions are most useful for mobile web developers, a number of people suggested that there should be a separate page to list these.

My personal list is as follows:

Web Developer Toolbar

Chris Pederick's toolbar isn't a mobile-specific extension but is nonetheless extremely handy since it lets you do quite a few different things from seeing information about the current page to turning on and off various DOM elements. The page size indicator is particularly useful since it adds up

http://chrispederick.com/work/webdeveloper/

User Agent Switcher Extension

This extension lets you set up your Firefox to send headers of your choice in each request it makes such that the browser looks like a different browser to the web server. This is very useful means for looking at sites that use device detection to serve specific versions of a site. I have mine set up to emulate a couple of popular phones.

http://chrispederick.com/work/useragentswitcher/

wmlbrowser Extension

This extension lets Firefox display WML 1.x markup which is something it can't normally do. This is useful for testing older mobile sites that use WML rather than XHTML. By the way, the desktop version of Opera supports WML natively, making it a very handy tool to keep around.

http://wmlbrowser.mozdev.org/

XHTML Mobile Profile Extension

Firefox can't handle the mime-type application/vnd.wap.xhtml+xml which is one of the possible mime-types for XHTML Mobile Profile, and which is supported by most phones. This extension adds support for this mime-type. (The other, application/xhtml+xml, is supported natively by Firefox.)

https://addons.mozilla.org/firefox/1345/