function startVideo(welke){
	document.getElementById("videoblock").style.display="";
	document.getElementById("videocontainer").style.display="";
	document.getElementById(welke).style.display="";	
}
function exitVideo(welke2){
	document.getElementById(welke2).style.display="none";
	document.getElementById("videocontainer").style.display="none";
	document.getElementById("videoblock").style.display="none";
}