AJS is a ultra lightweight JavaScript library that is around 1 and half year old. It is hugely inspired by MochiKit, but differs by being small. The current version is only 33 KB (uncompressed), whereas MochiKit is over 100 KB
integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.