function check(){
	var username = document.form1.userName.value;
	var userpwd = document.form1.userPwd.value;
	var checkcode = document.form1.checkcode.value;
	if(username == ""){
		alert("请输入用户名!");
		return false;
	}
	if(userpwd ==""){
		alert("请输入密码!");
		return false;
	}
	if(checkcode == ""){
		alert("请输入验证码");
		return false;
	}
}