<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8>
<style>
body {
font: 20px/1 monospace;
}
.float {
float: left;
width: 15ch;
height: 150px;
background: silver;
}
.mask {
width: 15ch;
height: 150px;
background: green;
position: absolute;
left: 15ch;
}
.test {
width: 28ch;
background: red;
}
</style>
</head>
<body>
<p>There should be no red:</p>
<div class="float">
<div class="mask"></div>
</div>
<p class="test">
Lorem ipsum dolor <span>sit</span> amet consectetur adipisicing elit.
</p>
</body>