我的表单上有一个包含错误消息的“div”标签。单击按钮且输入为空时显示此标签。我的代码正在运行，但是“div”标签正在快速隐藏。
<htlm>
<head>
</head>
<body>
<div id="ShowError">
<h3>Username Or Password is incorrect.</h3>
</div>
<form id="Main" method="POST">
<input id="User" type="text" name="Name" placeholder="Enter Your Username">
<br>
<input id="Pass" type="password" name="Pass" placeholder="Enter Your Password"/>
<br>
<button id="bt">Login</button>
<button >Cancel</button>
</form>
</body>
<script src=""></script>
</html>
div#ShowError{
opacity:0.0;
}
var btn = document.getElementById("bt");
btn.addEventListener("click",func);
var Username = document.getElementById("User");
var Password = document.getElementById("Pass");
function func()
{
if(Username.value == "" || Password.value == "")
{
document.getElementById("ShowError").style.opacity = "1.0";
}
}