function openPresentation() {
	var mypage = "/presentation.html";
	var myname = "presentation";
	var features = "";
	var w = 800;
	var h = 600;
	if(screen.width){
		var winl = (screen.width-w)/2;
		var wint = (screen.height-h)/2;
	} else{winl = 0;wint =0;}
	if (winl < 0) winl = 0;
	if (wint < 0) wint = 0;
	var settings = 'height=' + h + ',';
	settings += 'width=' + w + ',';
	settings += 'top=' + wint + ',';
	settings += 'left=' + winl + ',';
	settings += features;
	win = window.open(mypage,myname,settings);
	win.window.focus();
}