function openWindow(sUrl, sWindowName, aDimensions, sWinProps) {
			var sDimensions = '';
			var oNewWindow = new Object();
						
			if (aDimensions.length > 1) {
				sDimensions = 'width='+aDimensions[0]+',height='+aDimensions[1];
			}
			else if (aDimensions.length == 1) {
				sDimensions = 'width='+aDimensions[0]+',height='+aDimensions[0];
			}

			var iScrH = screen.availHeight;
			var iScrW = screen.availWidth;		
			var iTopLoc = (screen.availHeight/2) - (aDimensions[1]/2);
			var iLeftLoc = (screen.availWidth/2) - (aDimensions[0]/2);
			
			var $location = 'top=' + iTopLoc + ',left=' + iLeftLoc

			if (sWinProps == undefined) {
				sWinProps = 'toolbar=no,directories=no,location=no,status=no,menubar=no,resizable=no,scrollbars=no';
			}

			sWinProps += ',' + sDimensions + ',' + $location;

			oNewWindow = window.open(sUrl,sWindowName,sWinProps);
			
			if (oNewWindow == undefined) {
				alert('Er wordt geprobeerd om een pop-up venster te openen');
			}
			return false;
		}