css hover dropdown

html--------------------------

<div class="dropdown">
<span>鼠标移动到我这！</span>
　　<div class="dropdown-content">
　　<p>home</p>
　　<p>home1</p>
　　</div>
</div>

css---------------------------

.dropdown {
position: relative;
display: inline-block;
}
.dropdown-content {
display: none;
position: absolute;
background-color: #f9f9f9;
min-width: 160px;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
padding: 12px 16px;
animation:myfirst 5s;
-webkit-animation:myfirst 5s; /* Safari and Chrome */
}
.dropdown:hover , .dropdown-content {
display: block;
animation:myfirst 1s;
}

@keyframes myfirst
{
from {background: red;}
to {background: yellow;}
}

@-webkit-keyframes myfirst /* Safari 与 Chrome */
{
from {background: red;}
to {background: yellow;}
}