<!DOCTYPE html>
<p>Test adding a ::before pseudo element.</p>
<p>There should be two rectangles with identical sizes below. The first one should be yellow
    with some dots inside. The second one should be blue with nothing inside.</p>
<div style="line-height:100px; background:blue;">
    <div style="background:yellow;">..........</div>
    <br>
</div>
