mypage.css

* {
    box-sizing: border-box;
}

ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: #333;
}

li {
    float: left;
}

li a {
    display: block;
    color: white;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}

li a:hover:not(.active) {
    background-color: #111;
}

.active {
    background-color: #4CAF50;
}
/* Create three equal columns that floats next to each other */
.column {
    float: left;
    width: 33.33%;
    padding: 15px;
}

/* Clear floats after the columns */
.row:after {
    content: "";
    display: table;
    clear: both;
  
}
h2,p{
  text-align:center;
}
.footer {
    background-color: gray;
    padding: 10px;
    text-align: center;
}
#nav {
                list-style: none;
                float: left;
                 position: fixed;
                   width: 100%;
                  height: 50px;
                background-color: rgba(0,0,0,.5);
                      z-index: 99;
                   text-align: center;
            }

            #nav li {
                float: left;
                display: block;
                height: 40px;
                width: 200px;
                text-align: center;
                line-height: 40px;
                font-family: 'Roboto', sans-serif;
                font-weight: 700;
              font-size:21px;
                box-sizing:border-box;
                color:white ;

              
  
            }