*{margin:0;padding:0;box-sizing:border-box;font-size:0;}  
    nav a{
          text-decoration:none;
          color:inherit;
          font-size:14px;
          }
                
    nav li{
          display:inline-block;
          width:150px;
          height:30px;
          padding:5px 10px;
          background-color:#000;
          border:1px solid #000;
          text-align:center;
          color:#fff;
          position:relative;
    }
                
    nav li:hover{
          background-color:#fff;
          color:#000;
          }
                
    nav li>ul{
          display:none;
          }
    
    nav li:hover>ul{
          display:block;
          position:absolute;
          top:30px;
          left:0px;
    }