function dRollOver(t,w) {
	var src = document.getElementById(t.id+'_img').src;
	document.getElementById(t.id+'_img').src = src.replace((w?'_off':'_on'),(w?'_on':'_off'));
}

function challenge(){ 
	var popTop = (screen.height - 640)/2;
	var popLeft =(screen.width - 500)/2;
	var win=window.open("challenge/","loading","scrollbars=no,resizable=no,top="+popTop+",left="+popLeft+",width=640,height=500");
	win.focus();
}