ul#menu li{
    display: inline-block;
    font-size: 1.25em;
    width: 33%;
    margin: 0;
    padding:0;
    text-align: center;
}
ul#menu li a{
    color: #f5f5f5;
    text-decoration: none;
    border-bottom: 1px solid transparent;
}
ul#menu li a:hover{
    border-bottom: 1px solid;
}

ul#menu li a:hover:after, ul#menu li a:hover:before {
    top: 100%;
    left: 50%;
    border: solid transparent;
    content: " ";
    height: 0;
    width: 0;
    position: absolute;
    pointer-events: none;
}

ul#menu li a:hover:after {
    border-color: rgba(126, 175, 185, 0);
    border-top-color: #7eafb9;
    border-width: 10px;
    margin-left: -10px;
}
ul#menu li a:hover:before {
    border-color: rgba(238, 238, 238, 0);
    border-top-color: #eeeeee;
    border-width: 11px;
    margin-left: -11px;
}