html, body {
    background: #eaeaea;
}
#instafeed {
    margin: 0 0.5em;
}
#instafeed a {
    margin: 0;
    position: relative;
    overflow: hidden;
    display: inline-block;
    width: calc(100% / 5);
    transition: all .3s;
    height: 180px;
    background-size: cover;
}

#instafeed a:hover{
  opacity: .6;
}