Here are some of my favourite tools aimed at Web developers.
YSlow analyzes web pages and tells you why they're slow based on Yahoo’s rules for high performance web sites. YSlow is a Firefox add-on integrated with the popular Firebug web development tool. YSlow gives you:
There are two main features on this site. The first let you measure your Website performance. The script fully emulates natural browser behaviour downloading your page with all the images, CSS, JS and other files – just like a regular user. The second let you measure a network performance in terms of packets loss and ping speeds.
Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP(S) traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.
Fiddler is freeware and can debug traffic from virtually any application, including Internet Explorer, Mozilla Firefox, Opera, and thousands more.
The opinions expressed herein are my own personal opinions and do not represent
my employer's view in any way.