function CheckAll()
{
    var objUserName = document.getElementById("txtUserName");
    var objUserPwd = document.getElementById("txtUserPwd");
    var objVlidCode = document.getElementById("txtVlidCode");
    
    if (objUserName != null && objUserPwd != null && objVlidCode != null)
    {
        if (objUserName.value == "")
        {
            alert("请输入用户名");
            return false;
        }
        
        if (objUserPwd.value == "")
        {
            alert("请输入密码");
            return false;
        }
        
        if (objVlidCode.value == "")
        {
            alert("请输入验证码");
            return false;
        }
        
        return true;
    }
}