As a website developer, Firebug is the most useful add-on. A lot of things you can do with it such as
Inspect and edit HTML
Tweak CSS
Visualize CSS
Monitor your network activity to see how many files loaded
Debug and profile javascript
Quickly find errors
Explore the dom
Execute JavaScript on the fly
Logging for JavaScript
and more
Let me show how to install Firebug on Firefox and Chrome.

If you usually use Firefox, you can easily install it. Here is the step
1. Go to this link from your Firefox Browser
2. Click download
3. Firebug automatically be installed into your Firefox

Firebug is also available for Chrome but it is the lite version. Here is the step to install it for Chrome
1. Go to this link from your Chrome Browser
2. Click Install on that page
3. Firebug automatically be installed into your Chrome
Hope this post is useful for you. ^_^


Ileane
Mar 11. 2010
I’m a huge fan of Chrome, but I’ve never tried FireFox.
I’m not a webmaster, but maybe I’ll pick up on some CSS by using this extension. I’ll check out some of your other Chrome posts too.
Thanks!
@Ileane
deerawan
Mar 15. 2010
Yes Ileane, Chrome is really simple and elegant
Thanks for coming here.
Abby Canoy
Apr 07. 2010
You made some good points there. I did a search on the topic and found most people will agree with your blog.