function tr()
{
	var ev=eval(document.body.clientHeight-document.getElementById('main').offsetTop-document.getElementById('foot1').offsetHeight-document.getElementById('foot2').offsetHeight);
	if (ev<0) {
		document.getElementById('main').style.height=0;
	}
	else {
		document.getElementById('main').style.height=ev;
	}
	document.body.style.visibility = 'visible';
}