<!DOCTYPE html>
<html>
    <head>
        <script>
            window.onload = function() {
              document.body.offsetWidth;
              document.getElementById("foo").style.top = "200px";
            };
        </script>
    </head>
    <body style="font-size: 0"><span id="foo"><span style="position: relative; top: inherit; display: block; font-size: medium">This text should be 200px from the top of the body</span></span></body>
</html>