API:
<code language = "javascript">
HTTPRequest.buildQuery(queryData)
</code>
Builds a query in the form of ?key=value&key=value... from an assocaitive array / hash  table / whatever you feel like calling it today.
<code language = "javascript">
HTTPRequest.getXMLObject()
</code>
Gets a raw XMLHttpRequest object in a platform-agnostic way
<code language = "javascript">
HTTPRequest.genericRequest(method, uri, content, callback, fallback)
</code>
Performs a genericized HTTPRequest.
method: 
<blockquote>should be "GET", "POST", "HEAD", orany other method your server handles.</blockquote>
uri:
<blockquote>The page to pull.  Any get/head style queries should be appended as they would be in your address bar.</blockquote>
content:
<blockquote>String representing fully escaped form data for POSTing.  Will be ignored if method is not POST.  Comment if you believe this to be bad.</blockquote>
callback / fallback:
<blockquote>Functions in the form of myFunc(xmlObject).  These will be called if the request succeeds or fails, respectively.</blockquote>
<code language="javascript">
HTTPRequest.GET / HTTPRequest.HEAD (uri, queryData, callback, fallback)
</code>
uri:
<blockquote>The page to pull.  Please use the next parameter for GET/HEAD queries</blockquote>
queryData:
<blockquote>Assocaitive array of query data.</blockquote>
callback / fallback: 
<blockquote>same as in genericRequest</blockquote>
<code language="javascript">
HTTPRequest.POST(uri, queryData, formData, callback, fallback)
</code>
Similar to GET.  formData is an associative array of form variables.

Now, for the code!
<code language="javascript">
var HTTPRequest=Object();
if (window.location.toString().substr(0,5).toLowerCase()=="file:")
	alert("XMLHttpRequest, cannot work\n"+
				"from a local filesystem.\n"+
				"Please upload your project to\n"+
				"a webserver and try this again.");

HTTPRequest.buildQuery = function (query) {
	var data="";
	var first="?";
	for (i in query) {
		data+=first+escape(i)+"="+escape(query[i]);
		first="&";
	}
	return data;
}

HTTPRequest.getXMLObject = function () {
	if (typeof(XMLHttpRequest)!='undefined') return new XMLHttpRequest();
	var ax=['Msxml2.XMLHTTP.6.0', 'Msxml2.XMLHTTP.4.0',
					'Msxml2.XMLHTTP.3.0', 'Msxml2.XMLHTTP', 
					'Microsoft.XMLHTTP'];
	for (var i=0; i<ax.length; i++)
		try { 
			return new ActiveXObject(ax[i]); 
		} 
		catch (e) {}
	return null;
}

HTTPRequest.genericRequest = function (
	method, 
	uri, 
	content, 
	callback, 
	fallback) {
	var xmlhttp=HTTPRequest.getXMLObject();
	if (xmlhttp==null) {
		if (!HTTPRequest.complainedLoudly) 
			alert("Your browser does not support\n"+
						"XMLHttpRequest in any known form");
		HTTPRequest.complainedLoudly=true;
		return false;
	}
	xmlhttp.onreadystatechange=function () {
		if (xmlhttp.readyState==4) 
			if (xmlhttp.status==200) 
				callback(xmlhttp);
			else 
				fallback(xmlhttp);
	}
	if (method=="POST") {
		xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
		xmlhttp.setRequestHeader("Content-length",postdata.length);
		xmlhttp.setRequestHeader("Connection","close");
	} else content="";
	xmlhttp.open(method.toUpperCase(),uri,true);
	xmlhttp.send(content);
	return true;
}

HTTPRequest.GET = function (url, query, callback, fallback) {
	return HTTPRequest.genericRequest(
		"GET",
		url+HTTPRequest.buildQuery(query),
		"",
		callback,
		fallback);
}

HTTPRequest.HEAD = function (url, query, callback, fallback) {
	return HTTPRequest.genericRequest(
		"HEAD",
		url+HTTPRequest.buildQuery(query),
		"",
		callback,
		fallback);
}

HTTPRequest.POST = function (url, query, form, callback, fallback) {
	return HTTPRequest.genericRequest(
		"POST",
		url+HTTPRequest.buildQuery(query),
		HTTPRequest.buildQuery(form).substr(1),
		callback,
		fallback);
}
</code>