Hey, Web coders! For performance testing it’s hard to beat URIValet.com. Not only does it show crunchy stuff like “Server Header Details,” it also lists your download times across the board of connections from 56k to 6 Mbps, displays interactive charts of your page elements, lists your internal and external links (in separate tables), and provides a handy interface for validating your XHTML and CSS.
URIValet.com is now my first stop for performance and error checking. It also allows you to check the performance on any other page on the Web, which could well be educational. I recommend you give them a try (and drop them a donation for their work).