function PopUpValue(url,w,h) {
	var t = screen.availHeight/2 - h/2;
	var l = screen.availWidth/2 - w/2;
	var opties = "toolbar=no,location=no,status=no,menubar=no,scrollbars=yes,resizable=no,width=" + w + ",height=" + h + ",left=" + l + ",top=" + t;
	var newWindow = window.open(url, 'popup', opties);
}

function numberFilter() { 
	if (window.event.keyCode<48 || window.event.keyCode >57) {
	    window.event.keyCode = 0;
	}
}

function checkNumbers(value) {
	if (!isNaN(value) && value.indexOf('.') == "-1") {
	    return value;
	} else
	  	alert("Alleen (hele) getallen, zonder komma's en punten invoeren a.u.b. ");
	    return '';
}

function checkNumbersDec(value) {
	if (!isNaN(value)) {
	    return value;
	} else
	  	alert("Alleen getallen zonder komma's invoeren a.u.b. Een punt gebruiken is wel toegestaan. ");
	    return '';
}

function logout() {
	if (confirm("U wilt stoppen? "))
		top.location="logout.php?actie=logout";
  	return false;
}

function confirmTxt(txt,url) {
	if (confirm(txt))
		top.location=url;
	return false;
}