mozilla/pdf.js — pull request #1693 by benbro (2012-05-12 00:43:59+00:00)
Title: Use a reusable style sheet instead of creating a new tag for each rule.

IE9 breaks when creating too many style tags in one page:
http://support.microsoft.com/kb/262161

In any case, on all browsers it's better to reuse a single style sheet than creating a new one for each new rule.