var ie_value = 450 + 26;
var mozilla_value = 435 + 26;

if(window.innerHeight) {
	var new_height = window.innerHeight - mozilla_value;
} else if(document.body && document.body.offsetHeight) {
	var new_height = document.body.offsetHeight - ie_value;
}

document.write('<style>.mainframe_height { height: ' + new_height + 'px; }</style>');