Years ago I used OpenSTA to perform load and performance tests for web applications. I remember that it offered great recording possibilities which enabled us to quickly create new test scripts. Unfortunately it's a bit outdated, hence I'm a bit skeptic if it still works correctly with todays browsers.
Please let me which tools you recommend. Free tools are clearly preferred ;)
Note: The "to be tested" app is served over HTTP and uses jQuery and CSS.
My first preferences is Jmeter. ( http://jakarta.apache.org/jmeter/ ) It can capture ajax POST/GET, stress testing static assets, you can run it on multiple hosts, etc.
Go to youtube and search for Jmeter for easy to follow setup guide.
Grinder tool is quite useful.
http://grinder.sourceforge.net/
Generally good for most load testing. It's java based, so you need to keep an eye on the level of GCs the tool experiences (nothing like tool error messing with your results).