<!DOCTYPE html>
<html>

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

<body>

  <math style="position: absolute; top: 0; left: 0;">
    <mspace width="50px" height="3em" depth="3em" mathbackground="red"/>
    <mspace width="40px" height="1em" depth="2em" mathbackground="green"/>
    <mspace width="30px" height="2em" depth="1em" mathbackground="blue"/>
  </math>

</body>

</html>