Edit in JSFiddle

body {
    background: #cfcfcf;
}

ul {
    padding: 0;
    list-style: none;
}

li {
    position: relative;
    float: left;
    padding: 15px;
    background: white;
    border-right: 1px solid #cfcfcf;
}

li:last-child {
    border-right: 0;
}

li:after {
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 0;
    margin-left: -10px;
    border-left: 10px solid transparent;
    border-right: 10px solid transparent;
    border-bottom: 10px solid;
    color: #cfcfcf;
    content: '';
}

li:hover:after {
    color: firebrick;
}

<ul>
    <li>Uno</li>
    <li>Zwei trois</li>
    <li>Four</li>
    <li>Cinque Seks</li>
</ul>