<select></select>
. li {
position: relative;
}
li:hover:after,
li.active:after {
display: block;
}
li:after {
position: absolute;
top: 50%;
right: 0;
display: none;
margin-top: -10px;
width: 0px;
height: 0px;
border-width: 10px 20px 10px 0;
border-style: solid;
border-color: transparent #ffffff transparent transparent;
content: "";
}