That is a poor site to use to test your speed. They are selling their own connections, and so they throttle down the throughput to make you feel like you're getting gypped.
For an unbiased test, go to astound.net and click on "home services, and then speed test. The number will be different each time you run it.
They actually are the same for me every time I use it and it is on par with every other site I have tested my speed on.
Actually I just checked and that site isnt selling anything, now google ad's is advertising services but the site itself isnt selling anything.
The website you linked is selling services as well.
Here's the three I use:
http://test.lvcm.com/
http://us.mcafee.com/root/speedometer/default.asp
http://performance.toast.net/
At speedtest, I got 2526/419, and at my ATT-Yahoo, I got 2544/440. Pretty close.
Strange, but, to me, astound.net looked like they were touting their own stuff.