Learn Javascript

DOM Scripting by Jeremy Keith

I've had great success learning through the O'Reilly books, but after smashing my head against the O'Reilly Javascript book and getting absolutely nowhere, this book was a breath o fresh air. Jeremy Keith will get you started with Javascript quickly and put you on the right track.

Bulletproof AJAX by Jeremy Keith

This is the next step after DOM Scripting, it's a slim book which teaches you the basics o AJAX.

an easy way to insertAfter()

When you get through the DOM Scripting book and start to create your own nodes you'll notice there isn't an insertAfter() function in javascript, here's an easy way to get around it.