Web Developer Tools

I found some pretty cool tools for web developers.  If you are interested in what your web app is doing, where it is spending its time, areas for improvement, etc., take a look at the following...

1. Firebug
2. Page Speed
3. YSlow
4. HttpWatch [Update]

Page Speed and YSlow need Firebug (a Firefox plugin) to work.  Firebug is very impressive with all the details it provides and ability to inspect and alter the page.  Both Page Speed and YSlow give a type of rating for a page and offer advice for areas of improvement.

I'm not sure which one I like best, but no doubt Firebug is pretty amazing.  I took a look at msfast which is a tool born out of Myspace.  I couldn't find enough information about it and usage docs were almost non-existent so I decided to give up and pursue the others mentioned above.

I'll post with an update when I find which one provides the best information based on what I'm trying to do at the moment.

Update:  I actually went with all of them, but Firebug and HttpWatch helped the most for what I was doing.  A plus about HttpWatch... it works on IE (even though I don't like IE, but I really needed to use it for this exercise if possible) and it also works on Firefox.