Ajax HTTPPost javascript function

I'm developing an AJAX chat client for fun and I've come across a lot of issues with XMLHttpRequest.

First off, every access of the object should be in a try catch block, as exceptions can be thrown (especially with the send method) for no decipherable reason. You should handle these errors as well (a failed send will require recreation of the XMLHttpRequest object... for some reason trying to reuse them presents problems). I just have a function that creates the object and call it as needed.

Here is some code for initializing a more cross-browser XMLHttpRequest object which can be thrown into a function:

	var xmlhttp;
	/*@cc_on @*/
	/*@if (@_jscript_version >= 5)
	// JScript gives us Conditional compilation, we can cope with old IE versions.
	// and security blocked creation of the objects.
		try {
		xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
		try {
		xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
		} catch (E) {
		xmlhttp = false;
		}
		}
	@end @*/
	
	if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
		xmlhttp = new XMLHttpRequest();
		xmlhttp.overrideMimeType('text/xml');
	}

I honestly don't think AJAX is ready yet (for whatever), but I thought I would try to be somewhat informative.

Depending on how often you poll for data I can see it not being an issue.

I had mine going with 50ms delays and left it overnight before I saw the errors start to pop up. Call me crazy =\

Committed to HEAD.