var xmlHttp=null;
function showScreen(str) {
    var url="view_image.php";
    if (str.length == 0) { 
        document.getElementById("screen").innerHTML="";
        return;
    }
    xmlHttp=GetXmlHttpObject();
    if (xmlHttp==null) {
        alert ("Your browser does not support AJAX!");
        return;
    }
    else {   
        url=url+"?m="+str;
        xmlHttp.onreadystatechange=stateChanged;
        xmlHttp.open("GET",url,true);
        xmlHttp.send(null);
    }
}

function stateChanged() { 
    if (xmlHttp.readyState == 4) { 
        document.getElementById("screen").innerHTML=xmlHttp.responseText;
    }
}

function GetXmlHttpObject() {
	try  {
		// Firefox, Opera 8.0+, Safari
		xmlHttp=new XMLHttpRequest();
	}
	catch (e) {
		// Internet Explorer
		try {
			xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e) {
			xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
		}
	}
	return xmlHttp;
}