<!DOCTYPE html>
<style>
#container {
    width: 200px; height: 50px;
    background-color: orange;
    position: relative;
}

.square {
    position: absolute;
    top: 0;
    left: 0;
    width: 50px;
    height: 50px;
    background-color: blue;
}

.second {
    left: 100px;
}
</style>
<p>You should see four equally sized squares below. Two blue, and two orange.</p>
<div id="container">
    <div class="square"></div>
    <div class="second square"></div>
</div>