//function makeHttpRequest(url, callback_function, return_xml)
function makeHttpRequest(url, callback_function, return_xml, posdata)
{
    var http_request = false;

    if (window.XMLHttpRequest) { // Mozilla, Safari,...
        http_request = new XMLHttpRequest();
        if (http_request.overrideMimeType) {
            http_request.overrideMimeType('text/xml');
        }
    } else if (window.ActiveXObject) { // IE
        try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
        }
    }

    if (!http_request) {
        alert('Unfortunatelly you browser doesn\'t support this feature.');
        return false;
    }
    http_request.onreadystatechange = function() {
        if (http_request.readyState == 4) {
            if (http_request.status == 200) {
                if (return_xml) {
                    eval(callback_function + '(http_request.responseXML)');
                } else {
                    eval(callback_function + '(http_request.responseText)');
                }
            } else {
                //alert('There was a problem with the request.(Code: ' + http_request.status + ')');
            }
        }
    }
	if (!posdata) {
		http_request.open('GET', url, true);
		http_request.send(null);
	}
	else {
		http_request.open('POST', url, true);
		http_request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded")
		http_request.send(posdata);		
	}
}