function log_out()
{
//如果只有一个页面的话
//        htmain = document.getElementsByTagName("html"); 
//        htmain[0].style.filter = "progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)";

//如果是框架页的话
        var s = window.parent.frames;
        for (i = 0 ; i < s.length; i++){
                s.document.getElementsByTagName("html")[0].style.filter = "progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)";
        }
        if (confirm('你确定要退出？'))
        {
                return true;
        }
        else
        {
                var s = window.parent.frames;
                for (i = 0 ; i < s.length; i++){
                        s.document.getElementsByTagName("html")[0].style.filter = "";
                }
                return false;
        }
}