* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.main-nav {
    margin-top: 10px;
    list-style: none;
    padding-left: 0;
    background-color: #13a4a4;
}

.main-nav-item {
    display: inline-block;
    border-right: 1px solid #ffffff;
}

.main-nav-item a {
    color: white;
    padding: 2px 8px;
    text-decoration: none;
    border-radius: 2px;
}

.main-nav-item a:hover {
    color: blue;
}

.main-nav-item a:active {
    color: chocolate;
}

main {
    width: 98%; 
    height: 500px;
    border: 10px solid grey;
}