<p>I need a tool to measure a website's performance that's free and does not require any changes to be made to the code (jsp asp pages). All help is appreciated.</p>

For performance measurement I recommend you
YSlow
, it's a Firefox add-on integrated with
Firebug
, it analyzes your web pages and tells you why they're slow based on the
rules for high performance web sites
.
Screenshot
Also with the Firebug Network Monitoring tab, you can see which resources are taking more time and bandwidth to download:
(source:
getfirebug.com
)