"Web 2.0" start, web developers need to learn ajax. Is not afraid of things - Ajax is very easy to learn smile.gif If a programmer has managed to understand php, ajax will be even easier.

On dynamic web content to modify the JavaScript is very well explained in this paragraph on the DOM:
http://www.musestorm.com/developers/..._tutorial2.jsp

And there certainly find the proper ajax tutorial:
http://www.w3schools.com/Ajax/default.asp
http://www.xul.fr/en-xml-ajax.html
http://www.ajaxtutorial.net/
http://www.ajaximpact.com/tutorials.php