Ajax Drop Down Menus
Here is a nice little tutorial on using Ajax to create drop down menu boxes. Adam does a good job of walking through the easy development of this and supplies us with samples and source code.
In our example, we’ll use a pair of dropdown menu boxes (SELECT tags in HTML). A selection in the first box affects our list of choices in the second box. It’s not exactly cutting edge (Thau did something similar using JavaScript), but it’s a proof of concept.
Link : Nitty Gritty Ajax: by Adam DuVander 12 Apr 2006