function setOpacity(obj,value) {
	obj.style.opacity = value/10;
	obj.style.filter = 'alpha(opacity=' + value*10 + ')';
}

function centerAndShow(obj)
{
	var cw = obj.offsetWidth;
	var ch = obj.offsetHeight;
	var pr = obj.parentNode;
	var pw = pr.offsetWidth;
	var ph = pr.offsetHeight;
	//alert(pw+" | "+ph);
	//alert(cw+" | "+ch);
	obj.style.left=(pw/2)-(cw/2)+"px";
	obj.style.top=(ph/2)-(ch/2)+"px";
	document.getElementById('overlay').style.left="0px";
}

function hideObject(obj)
{
	obj.style.left="-10000px";
	document.getElementById('overlay').style.left="-10000px";
}

function addAnswer()
{
	var r = document.createElement("input");
	r.type="text";
	r.style.width="70%";
	r.name="answers[]";
	document.getElementById('answerslist').appendChild(r);
	var v = document.createElement("select");
	v.name="correct[]";
	document.getElementById('answerslist').appendChild(v);
	var cy = document.createElement("option");
	cy.value="false";
	cy.innerHTML="Onjuist";
	v.appendChild(cy);
	var cn = document.createElement("option");
	cn.value="true";
	cn.innerHTML="Juist";
	v.appendChild(cn);
	//document.getElementById('answerslist').innerHTML += "<input type=\"text\" style=\"width: 70%;\" name=\"answers[]\"\">&nbsp;<input type=\"checkbox\" name=\"correct[]\"><br>";
}