What is prototype.js? Is that a third party library?

prototype is a js framework, which can be downloaded from http://prototype.conio.net/

Regards,
Kumar S
GuyFromChennai.com

From my understanding, AJAX is supported on every browser which has JavaScript Support, and if the browser is Internet Explorer, it would need to be version 5 or above.

The code you have provided merely tests if support for that version of AJAX will work in the browser, rather than if AJAX works at all, as there are multiple methods of making use of AJAX.

It's a nice bit of code to know, but maybe you should amend the title of your snippet?