style.css

body {
    background-color: #EEE;
}

header {
    display: flex;
    justify-content: center;
}

button {
    background: none;
    color: inherit;
    border: none;
    padding: 0;
    font: inherit;
    cursor: pointer;
    outline: inherit;
}

button {
    margin-top: 10px;
    margin-right: 10px;
    padding: 15px 40px;
    font-size: 14px;
    line-height: 1em;
    text-shadow: 0 1px rgba(0, 0, 0, 0.4);
    color: white;
    display: inline-block;
    vertical-align: middle;
    text-align: center;
    cursor: pointer;
    font-weight: bold;
    transition: background 0.1s ease-in-out;
    -webkit-transition: background 0.1s ease-in-out;
    -moz-transition: background 0.1s ease-in-out;
    -ms-transition: background 0.1s ease-in-out;
    -o-transition: background 0.1s ease-in-out;
    text-shadow: 0 1px rgba(0, 0, 0, 0.3);
    color: #fff;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
    font-family: 'Helvetica Neue', Helvetica, sans-serif;
    background-color: #f06060;
    box-shadow: 0px 3px 0px 0px #cd1313;
    text-decoration: none;
}

button:hover {
    background-color: #ed4444;
}

button:active {
    box-shadow: 0px 1px 0px 0px #cd1313;
}

#About {
    background-color: #608ef0;
    box-shadow: 0px 3px 0px 0px #1364cd;
}

#About:hover {
    background-color: #449bed;
}

#About:active {
    box-shadow: 0px 1px 0px 0px #1364cd;
}

#Contact {
    background-color: #78f060;
    box-shadow: 0px 3px 0px 0px #13cd1c;
}

#Contact:hover {
    background-color: #60ed44;
}

#Contact:active {
    box-shadow: 0px 1px 0px 0px #13cd23;
}

#content {
    max-width: 80%;
    text-align: center;
    margin: 40px auto;
}