function sample(){ // updates user list on search
	var roll=document.getElementById('roll_number').value;
	var out=document.getElementById('school_combo');

	var req = createXMLHttpRequest();
	req.onreadystatechange = function() {
		if (req.readyState == 4 && req.status == 200) { 
			out.innerHTML = req.responseText; 
			if (out.innerHTML.length>0) out.style.display='';
			else out.style.display='none';
		}
	};
	req.open('GET', 'requests/school_lookup.php?roll='+roll, true);
	req.send(null);
}



function load_sensors_content(file, menuId){
	var content=document.getElementById('sensors_content');
	var menu_item = document.getElementById(menuId);
	var req = createXMLHttpRequest();
	
	//to remove the class on link items
	var items = document.getElementById('sensors_list');
	for (var i=0; i<items.childNodes.length; i++) {
		if(items.childNodes[i].nodeName=='LI') { // IE only sees LI, but other browsers don't
			items.childNodes[i].firstChild.className='';
		}
	}
	
	req.open('GET', 'content/sensors_content/get_sensor_content.php?file='+file+'&menuId='+menuId, true);
	req.onreadystatechange = function() {
		if (req.readyState == 4) { 
			content.innerHTML = req.responseText;
			menu_item.className = 'active';
		}
	};
	
	req.send(null);
}




// *** GENERAL ****************************************************************************************
function createXMLHttpRequest(){
	var types = ['Microsoft.XMLHTTP', 'MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP'];
	for (var i = 0; i < types.length; i++) { // if MSIE give him activeX
		try { return new ActiveXObject(types[i]); } catch(e) {}
	}
	try { return new XMLHttpRequest(); } catch(e) {} // if not MSIE - usual XHR
	return false; // XMLHttpRequest is not supported by browser
}

function progress(show){
	var dv=top.document.getElementById('progress');
	if (show) { dv.style.display=''; dv.style.visibility='visible'; }
	else { dv.style.display='none'; }
}