.dropbtn {
  background-color: #4CAF50;
  color: white;
  padding: 16px;
  font-size: 16px;
  border: none;
  cursor: pointer;
}

.dropdown2 {
  position: relative;
  display: inline-block;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  overflow:auto;
  width:100%;
  z-index: 1001;
}

.dropdown-content a {
  color: black;
  background-color:lightgrey;
  border-bottom:solid 1px black;
  border-right:solid 1px black;
  border-left:solid 1px black;
  padding: 12px 16px;
  text-align:center;
  text-decoration: none;
  display: block;
}
.dropdown-content a:first-child{
  border-top:solid 1px black;
}
.dropdown-content a:hover {
  color: white;
  background-color:dimgrey;
  text-decoration: none;
}

.dropdown2:hover .dropdown-content {
  display: block;
}

.dropdown2:hover .dropbtn {
  background-color: #3e8e41;
}

/*
<h1>下拉菜单</h1>

<p>请把鼠标移到按钮上，以打开下拉菜单。</p>

<div class="dropdown">
  <button class="dropbtn">Dropdown</button>
  <div class="dropdown-content">
  <a href="#">Link 1</a>
  <a href="#">Link 2</a>
  <a href="#">Link 3</a>
  </div>
</div>
*/