There are many useful Web development tools that integrate in your browser. These in-browser tools are commonly known as add-ons or extensions. Though add-ons and extensions aren’t just for Web development, many of them out there are designed specifically for Web developers. In-browser tools vary greatly in the jobs they perform; for example, some of them help you diagnose issues with CSS, HTML and JavaScript, while others evaluate the accessibility of your website.
In this article, we explore some of the most popular and useful in-browser Web development tools. You’ll find tools for popular Web browsers like Firefox and Internet Explorer. Whether you need to debug and inspect your HTML, inspect HTTP headers, access FTP source files, evaluate accessibility or just figure out what color a Web page element is, you may find a variety of tools discussed here useful.
http://www.smashingmagazine.com/2008/11/18/15-helpful-in-browser-web-development-tools/
