Firefox is one of the best tool available for web developers which equips the developer with code testing and debugging capabilities.
There are many useful firefox options and extensions that comes in handy during software development life cycle and in this article we will be listing few of useful plugins that we commonly use.
To find information related to the page that is getting displayed on the browser click Tools > Page info. This will give you permission settings of a page, security identity of the page, feed url and other page specific information like page content-type, encoding, meta tags used, cookie permission settings etc.
Web Developer extension
Added as a toolbar in firefox, this extension gives CSS related information, page information, outlines page elements, tab index, gives topographic information and many such details.