<!DOCTYPE html>
<style>
.clamp {
display: -webkit-box;
-webkit-box-orient: vertical;
-webkit-line-clamp: 5;
font: 16px / 32px serif;
background-color: yellow;
overflow: hidden;
}
</style>
<div class="clamp">
<div>
Line 1<br>Line 2<br>Line 3<br>Line 4<br>Line 5<br>Line 6
</div>
</div>