Вы можете написать класс как бутстрапе
body {
background-color: white;
font-family: PT Sans, sans-serif;
text-shadow: 1px 1px rgba(166,166,166,.2);
}
header {
background: white;
width: 100%
padding: 40px 0;
color: black;
text-align: center;
}
a {
text-decoration: none;
color: black;
font-size: 1.0em;
letter-spacing: 2px;
}
nav {
box-shadow: 1px 1px 10px rgba(166,166,166,.2);
}
nav ul {
background-color: rgba(253,235,193,.3);
overflow: visible;
color: white;
padding: 0;
text-align: center;
margin: 0;
position: relative;
}
nav ul li {
display: inline-block;
padding: 20px 40px;
position: relative;
}
nav ul ul {
display: none;
}
nav ul>li:hover {
background-color: rgba(253,235,193,.6);
text-align:center;
}
nav ul li:hover ul{
display: block;
margin-top: 20px;
}
nav ul li:hover li{
margin-left: -40px;
margin-top:-15px;
text-align: center;
float: left;
clear: left;
}
.portfolio_menu{position:absolute;top:100%;left:0;z-index:1000;display:none;float:left;min-width:160px;padding:5px 0;margin:2px 0 0;font-size:14px;text-align:left;list-style:none;background-color:#fff;-webkit-background-clip:padding-box;background-clip:padding-box;border:1px solid #ccc;border:1px solid rgba(0,0,0,.15);border-radius:4px;-webkit-box-shadow:0 6px 12px rgba(0,0,0,.175);box-shadow:0 6px 12px rgba(0,0,0,.175)}