<!DOCTYPE html>
<html>

<head>
    <title>mspace</title>
</head>

<body>

  <math style="position: absolute; top: 0; left: 0;">
    <mspace width="5em" height="10px" mathbackground="red"/>
  </math>

  <math style="position: absolute; top: 10px; left: 0;">
    <mspace width="60pt" height="10px" mathbackground="green"/>
  </math>

  <math style="position: absolute; top: 20px; left: 0;">
    <mspace width="5pc" height="10px" mathbackground="blue"/>
  </math>

  <math style="position: absolute; top: 30px; left: 0;">
    <mspace width="10ex" height="10px" mathbackground="red"/>
  </math>

  <math style="position: absolute; top: 40px; left: 0;">
    <mspace width="50px" height="10px" mathbackground="green"/>
  </math>

  <math style="position: absolute; top: 50px; left: 0;">
    <mspace width="1in" height="10px" mathbackground="blue"/>
  </math>

  <math style="position: absolute; top: 60px; left: 0;">
    <mspace width="2.54cm" height="10px" mathbackground="red"/>
  </math>

  <math style="position: absolute; top: 70px; left: 0;">
    <mspace width="25.4mm" height="10px" mathbackground="green"/>
  </math>

</body>

</html>
