Answers for "outline only on bottom css"

outline bottom css

div {
    width: 100px;
    height: 100px;
    background: #eee;
}
div:hover {
    width: 100px;
    height: 100px;
    background: #eee;
    border-bottom: 1px solid;
    margin-bottom: -1px;
}

put a border only on bottom

#element {
   border-bottom: 1px solid;
}