One of the fastest ways to find errors, copy layouts, check CSS and measure window or image size is though web browser. Our recent webmaster survey results shows that web developers definitely prefer Mozilla Firefox as default browser, so we decided to create an article and review some of the best and most essential add-ons for web developers.

Web Developer - various web developer tools related to cookies, CSS style information, web form inspection, images, code validation, DOM inspector, etc. Very useful tool favorite to many web developers.

Firebug - Firebug is very similar to Web Developer add-on, can do all above and inspect and see the changed done in the code in real time, code debugger is also included.

Window Resizer - test the webpage look at different screen sizes and resolutions. One of the best way to see how website will look on netbook or large screen monitor.

FireShot - entire and extensive snapshot of webpage. I use this one for presentations and including images on my portfolio page.

ColorZilla - Color picker add-on, very easy to use, can copy color information in many different color formats - RGB, HSL, CMYK and web format.

FireFTP - Platform independent FTP client at your Firefox Browser, offer many options including SSL/TLS/SFTP transfers, support directory integrity check, file comparison.

IE Tab - Check how website will look in IE, without need to open new browser. 

Page Diff - compare the source code of 2 different pages, helps to find code problems without need of debugging.

Measure It - Check sizes of images, web pages, layouts, etc.

YSlow - Website speed benchmark, including suggestions how to optimize and improve the speed of website.

This add-ons will definitely improve your performance as web developer and will make your work much easier.