Load-Time PHP or Plugin????

Does anyone know of a “load-time” plugin of some sort that would display the time (in seconds) your page loads?

Here’s an example:
http://www.contact-sheet.de/blog/

(scroll down the the bottom of the page and on the right hand side it says something like this:

WordPress took 1.496 seconds to generate this page.)

Everytime you refresh, the seconds change depending on how fast the page loads and stuff. I tried using PHP codes before but I’m not sure how to include it with WordPress and the codes for validation. (ex: put this function at the top of the page) when I do it (before the validation code) it gives me errors and stuff. Help? =)