function validMail()
{
    var username=document.getElementById("username1").value;
    var password=document.getElementById("password1").value;
    if(username=="")
    {
        alert("用户名不能为空！");
        document.getElementById("username1").focus();
        return false;
    }

    if(password=="")
    {
        alert("密码不能为空！");
        document.getElementById("password1").focus();
        return false;
    }
    document.getElementById("username1").value="";
    document.getElementById("password1").value="";
    return true;
}

//同步修改隐藏区域内容
function changeValue(obj1,obj2)
{
    document.getElementById(obj2).value=document.getElementById(obj1).value;
}