But there is one problem with most of the current implementations of Ajax: it has one dependency, and that is the XmlHttpRequest object. Most modern browser, like Firefox, have inbuilt support for this object, but older browsers, like Internet Explorer 6, don’t have native support for this object. Luckily, IE 6 does support it, but it’s built in as an ActiveX control, which means your visitors get an ugly warning message about the possible danger of an ActiveX control, or in some cases it just doesn’t work at all.
In this tutorial, I will show you how to use Ajax without even having to use the XmlHttpRequest object.
Read the article: PHPit – Totally PHP – Ajax & PHP without using the XmlHttpRequest Object
Via digg where there’s some good discussion going on about this technique.