function reqType(){
	// branch for native XMLHttpRequest object
    if(window.XMLHttpRequest) {
    	try {
			req = new XMLHttpRequest();
        } catch(e) {
			req = false;
        }
    // branch for IE/Windows ActiveX version
    } else if(window.ActiveXObject) {
       	try {
        	req = new ActiveXObject("Msxml2.XMLHTTP");
      	} catch(e) {
        	try {
          		req = new ActiveXObject("Microsoft.XMLHTTP");
        	} catch(e) {
          		req = false;
        	}
		}
    }
    return req;
}
function chkDB(poststr){
	
	var httpRequest = reqType();
	httpRequest.onreadystatechange = processRequest;
	httpRequest.open('POST', 'confirm.php', false);
	//this line is very important to send a form with post method
	httpRequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
	httpRequest.send(poststr);
	function processRequest() {
	if (httpRequest.readyState == 4) {
            if (httpRequest.status == 200) {
                var dvalue = httpRequest.responseText;
            } else {
                return false
            }
        }
    }
    var dvalue = httpRequest.responseText;
	return dvalue;
}