var http_request1 = false;
//var http_request2 = false;
//var http_request3 = false;
//var http_request4 = false;

function make_http_request_obj(){
    var http_request_obj = false;
    if (window.XMLHttpRequest) 
    { // Mozilla, Safari,...
        http_request_obj = new XMLHttpRequest();
        if (http_request_obj.overrideMimeType)
        {
                    
            //http_request.overrideMimeType('text/xml');
            http_request_obj.overrideMimeType('text/html');
        }
    }
    else if (window.ActiveXObject){ // IE
        try{
            http_request_obj = new ActiveXObject("Msxml2.XMLHTTP");
        }catch (e){
            try{
                http_request_obj = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
        }
    }
    if (!http_request_obj){
        alert('Cannot create XMLHTTP instance');
        return false;
    }
	return http_request_obj;
}
/////////////////////////////////////////////////////////////////////
function check_username(username){
    var params = "check_username=1&username="+username;
    url = 'handler.php';
    http_request1 = make_http_request_obj();
    http_request1.onreadystatechange = check_username_;
    http_request1.open('POST', url, true);
    http_request1.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    http_request1.setRequestHeader("Content-length", params.length);
    http_request1.setRequestHeader("Connection", "close");
    http_request1.send(params);
}
function check_username_()
{    
    if (http_request1.readyState == 4)
    {
        if (http_request1.status == 200)
        {
            var result = http_request1.responseText;

            if (result != null )
            {           
                if(result=='available'){
				document.getElementById("reg_usrname_msg").innerHTML="Congratulations! This username is available.";
				return false;
				} else {
				document.getElementById("reg_usrname_msg").innerHTML="Sorry! This username is not available.";				
				return false;
				}				
            }
        } else
        {
            alert('Error Occured while processing the Request');
        }
    }
}