My Top 10 Firefox Web Development Addons

Firefox is my primarily web development browser. For regular Internet browsing I use Google Chrome. 

As for today the following  Firefox addons I find very useful for my work.

1. Firebug - no need to describe this. Must have.
2. Page Speed - Firebug extension from Google, that helps to optimize page loading speed.
3. YSlow - Firebug extension from Yahoo to optimize page speed.
4. Web developer - lots of useful stuff.
5. HTML Validator - validates page according to W3C standard.
6. Copy Plain Text - helps to copy text without formatting.
7. SEOQuake - very useful plugin for SEO. I also install SEOQuake Yandex extension, which extends SEOQuake for Russian most popular search engine.
8. EditCSS - I use it sometimes, when I want to create new website or make mass CSS changes.
9. MeasureIt - measuring tool.
10. ColorZilla - color picker tool.