function getViewportDimensions() {
    var intH = 0, intW = 0;
    
    if(self.innerHeight) {
       intH = window.innerHeight;
       intW = window.innerWidth;
    } 
    else {
        if(document.documentElement && document.documentElement.clientHeight) {
            intH = document.documentElement.clientHeight;
            intW = document.documentElement.clientWidth;
        }
        else {
            if(document.body) {
                intH = document.body.clientHeight;
                intW = document.body.clientWidth;
            }
        }
    }

    return {
        height: parseInt(intH, 10),
        width: parseInt(intW, 10)
    };
}

function show_overlay() {
	//for(i=0; i<document.forms[0].elements.length; i++){
		//var ele = document.forms[0].elements[i];
		//if (ele.type == 'select-one') {
	   	//	ele.style.display='none';
	   	//}
	//}
  
	var viewport = getViewportDimensions();
	var y = (document.pageYOffset?document.pageYOffset:document.documentElement.scrollTop);
	var overlay = document.getElementById('overlay');  
	overlay.style.width = viewport.width + 'px'; 	
   	overlay.style.height = y + viewport.height + 'px';
	overlay.style.display='block';
}
function hide_overlay() {
	//for(i=0; i<document.forms[0].elements.length; i++){
	//   document.forms[0].elements[i].style.display='block';
	//}
	var overlay = document.getElementById('overlay');  
	overlay.style.display='none';
}
function show_message(element_id) {
	show_overlay();
	
	var element = document.getElementById(element_id);
	var width = parseInt(element.style.width);
	var height = parseInt(element.style.height);
	
	var viewport = getViewportDimensions();
	var y = (document.pageYOffset?document.pageYOffset:document.documentElement.scrollTop);
	
   	var left = (viewport.width == 0) ? 50 : parseInt((viewport.width - width) / 2, 10);
   	var top = (viewport.height == 0) ? 50 : parseInt((viewport.height - height) / 2, 10);
   	
   	element.style.left = left + 'px';
   	element.style.top = y + top + 'px';
	element.style.display='block';
}

function hide_message(element_id) {
	hide_overlay();
	document.getElementById(element_id).style.display='none';
}