//去除空格
    function trim(str)
    {  
        return str.replace(/(^\s*)|(\s*$)/g, "");
    }
    
    function checkLoginInput()
    {
        if(trim(document.getElementById('txtUserName').value)=='')
        {
            alert('请输入用户名！');
            document.getElementById('txtUserName').value='';
            document.getElementById('txtUserName').focus();
            return false;
        }
        if(document.getElementById('txtUserPwd').value=='')
        {
            alert('请输入密码！');
            document.getElementById('txtUserPwd').focus();
            return false;
        }
        return true;
    }