> [snip] > > You will only need JavaScript. > > That statement may not be true. For example the computation might have > to involve a database or web service lookup. > [/snip] > > True, and you will only need JavaScript, since Ajax essentially uses > JavaScript to perform the request, no? Only if the service returns JSON and you can use a dynamic script element[1]. If the service does not do that you will need a server side proxy script that allows you to reach outside your own Domain[2]. XMLHttpRequest, the driver of Ajax cannot reach scripts not on the same domain for security reasons. Dojo offered a way around that[3] in the newest version, using hidden iframes as the proxy which results in annoying click sounds in MSIE and might actually throw up more errors as we progress. Ajax is NOT client side, it is a middle tier between client and server side. [1] http://icant.co.uk/sandbox/jsonsearch/ [2] http://www.beginningjavascript.com/Chapter8/index.html (example "Retrieving external RSS feeds with PHP and XHR") [3] http://dojotoolkit.org/~jburke/XHRIFrameProxy.html -- Chris Heilmann Book: http://www.beginningjavascript.com Blog: http://www.wait-till-i.com Writing: http://icant.co.uk/