function log_out_comirm() {
	ht = parent.document.getElementsByTagName("body");
	ht[0].style.filter = "progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)";
	if (confirm('确定要退出系统登录？')) {
		return true;
	}
	else	{
		ht[0].style.filter = "";
		return false;
	}
}

function log_out(str) {
	if( log_out_comirm()) {
		parent.top.location.href=str;
	}
}