var xmlHttp;

function getXmlHttpObject( handler ) {
    var objXmlHttp=null

    if ( navigator.userAgent.indexOf( "Opera" ) >= 0 ) {
        alert( "This example doesn't work in Opera" )
        return
    }
    if ( navigator.userAgent.indexOf( "MSIE" ) >=0 ) {
        var strName="Msxml2.XMLHTTP"
        if ( navigator.appVersion.indexOf( "MSIE 5.5" ) >= 0 ){
            strName = "Microsoft.XMLHTTP"
        }
        try{ 
            objXmlHttp = new ActiveXObject( strName )
            objXmlHttp.onreadystatechange = handler
            return objXmlHttp
        }catch( e ) { 
            alert( "Error. Scripting for ActiveX might be disabled" )
            return
        }
    }
    if ( navigator.userAgent.indexOf( "Mozilla" ) >= 0 ) {
        objXmlHttp=new XMLHttpRequest()
        objXmlHttp.onload=handler
        objXmlHttp.onerror=handler
        return objXmlHttp
    }
}

function checkCaptcha(txtCaptcha) {
    var url = 'ajaxbroker.php?action=checkCaptcha&txtcaptcha=' + txtCaptcha;
    xmlHttp=getXmlHttpObject(handlecheckCaptcha);
    xmlHttp.open( "GET", url , false );
    xmlHttp.send( null );
}

function handlecheckCaptcha() {
	if ( xmlHttp.readyState==4 || xmlHttp.readyState=="complete" ) { 
		var text_msg = xmlHttp.responseText;
		var show_msg = "";
		if (text_msg!=""){
			show_msg += text_msg;
			//Get a reference to CAPTCHA image
			img = document.getElementById('imgCaptcha'); 
			//Change the image
			img.src = 'gen_image.php?' + Math.random();
		}
		if (show_msg!=""){
			document.getElementById('text_msg').innerHTML = "<b>"+show_msg+"</b>";
			document.getElementById('txtCaptcha').value = "";
		}else{
			document.getElementById('text_msg').innerHTML = "";
		}
	}
}