make an drodown menu code example

Example 1: make an drodown menu

/*The css file*/
nav {
  background-color: black;
  max-width: 300px;
  margin: 10px;
}
nav li ul {
  visibility: hidden;
  height: 0;
}
nav > ul > li:hover ul {
	visibility: visible;
  	height: 100px;
  	width: 60px;
  	transition-delay: 0.5s;
}

Example 2: make an drodown menu

<!--on the html document-->
<nav>
	<ul>
    	<li>
        <a href="#">Hello</a>
        	<ul>
            	<li>World!</li>
                <li>This is a dropdown</li>
            </ul>
        </li>
  </ul>
</nav>