Introduction to Ajax

http://javascriptsearch.com/guides/Beginner/articles/MasteringAJAX_1.html

讲得不错。特别是最后两段，是初学者的苦口良药：思考比copy & paste更重要！

For now, though, spend some time thinking about just how powerful Ajax applications can be. Imagine a Web form that responds to you not just when you click a button, but when you type into a field, when you select an option from a combo box...even when you drag your mouse around the screen. Think about exactly what asynchronous means; think about JavaScript code running and not waiting on the server to respond to its requests. What sorts of problems can you run into? What areas do you watch out for? And how will the design of your forms change to account for this new approach in programming?

If you spend some real time with these issues, you'll be better served than just having some code you can cut-and-paste and throw into an application that you really don't understand. In the next article, you'll put these ideas into practice and I'll give you the details on the code you need to really make applications like this work. So, until then, enjoy the possibilities of Ajax.