/* generieke popup functie	*/	
function popup(url,hoogte,breedte)	{
	var height, width;
	if (document.all)
	    height = document.body.offsetHeight, width = document.body.offsetWidth;
	else if (document.layers)
	    height = window.innerHeight, width = window.innerWidth;
		
	var y = (height/4)-0, x = (width/4)-0;
	
	popupvenster = window.open(url,"venster","width="+breedte+",height="+hoogte+",toolbar=0,scrollbars=no,directories=0,status=0,menubar=0,location=0,resizable=0,top=" + y + ",screenY=" + y + ",left=" + x + ",screenX=" + x);

}
		
		
/* show/hide layers */
		
function getStyle( layer ) {
	if( document.getElementById ) {
		return document.getElementById( layer ).style
		} 
	else if( document.all ) {
		return document.all[layer].style
		} 
	else {
		return document[layer]
		}
	}


function showLayer(laag)	{
	getStyle(laag).visibility = "visible";
	getStyle(laag).display = "inline";
	}
	
function hideLayer(laag)	{
	getStyle(laag).visibility = "hidden";
	getStyle(laag).display = "none";
	}