I've been playing with a fun little tool (its free), that I thought would be attractive to many people with a webpage. We are all quick to point the finger at the web host when our site not being up to snuff may be the culprit.
Many of us add plugins and widgets to our sites without considering the resultant implications to site load speed... which we all recognize as being vital in this day and age of instant gratifications.
FireBug lets you explore the far corners of the DOM by keyboard or mouse. All of the tools you need to poke, prod, and monitor your JavaScript, CSS, HTML and Ajax are brought together into one seamless experience, including a debugger, error console, command line, and a variety of fun inspectors. A must for every person concerned about optimizing their site's performance!
Firebug was written by Joe Hewitt, one of the original Firefox creators.
The Firebug plugin YSlow is a web development tool and analyzes web pages and tells you why they're slow based on the rules for high performance web sites. It offers
Performance report card
HTTP/HTML summary
List of components in the page
Tools including JSLint
http://www.joehewitt.com/software/firebug/
http://getfirebug.com/
Some Fun Features
Logging for web pages
Web developers have suffered with "alert debugging" for centuries. If you enjoy clicking the "Ok" button 40,000 times a day, FireBug is not for you. Otherwise, you'll enjoy having the ability to log messages from JavaScript in your web page directly to the FireBug console.
JavaScript Debugging
Want to stop your JavaScript and step through it line by line? No need to fire up a big fat debugger. FireBug includes a simple lightweight way to set breakpoints in your scripts and examine every step of execution.
Errors at your fingertips
Nobody likes to see errors in their web pages, but with FireBug you won't mind as much. FireBug adds a little icon to the Firefox status bar which tells you if your page is busted. Open up the FireBug panel and you're looking at the errors that occurred in that page, and only that page. No more digging through the muddy pile of errors in the JavaScript Console window.
Inspectors galore
Elements and styles and events, oh my. There's a lot going on behind the curtain of a web page. FireBug's inspectors let you stroll lazily through the DOM using the familiar hyperlink model of the web. If you see an object reference, you can click it to inspect it.
Command line
If you enjoy "alert debugging" then you probably also enjoy typing "javascript: " urls in the location bar all day. If not, then you'll enjoy using FireBug's JavaScript command line instead.
Ajax Request Spy
If you feel hip every time you fire off an XMLHttpRequest on your Ajax website, FireBug will secure your place amongst the avante garde. The FireBug console can log all Ajax request traffic as it happens, and allows you to inspect the responses.
Live Editing
It's no fun just looking at the DOM. FireBug's inspectors let you edit some parts of the DOM. More editing features to come in a future version...

Thu, 4 September 2008, 02:52
I use firebug constantly, it's great except for one fairly major issue, bear with me on this.
Imagine you've written a large javascript app, it's maybe 40k+ lines of code and you intend firebug to help you resolve an issue. This is how firebug is intended to be used.
I should say before I go on that my system isn't slow, it's a core2duo and I have 4GB of ram.
Now, you know roughly where your issue is so you set a breakpoint, refresh the page and do what it takes you to get to that section in code. Firebug breaks and you think you're off and running; hit the step into button and you wait.. and wait.. and wait, oh here we are. Hit step into again and wait.. and wait.. and wait.. and we arrive.
You see the problem - it's very slow at the job it was intended for. Now I know it's free and whatnot but all I'm saying is it can be annoying to work with. I'd hapily pay for a version that was faster (though a crippled slow free version would annoy me if they could do it).
Other than that it's a useful extension.