<!DOCTYPE html> <html> <head> <style id="firstLetterSheet"> .fl:first-letter { color: red } </style> <script> function boom() { document.getElementById("parent").className = ""; document.body.offsetWidth; document.getElementById("test").style.position = "relative"; } </script> </head> <body onload="boom()"> <div class="fl" id="parent" style="color: green"> Foo <span id="test">Bar</span> </div> </body> </html>