Synopsis says it all, default font size in JEditorPane is too small on Windows L&F. Problem is visible in SwingSet2 demo when viewing source code of demo and also hits Netbeans when Swing HTML browser (HtmlEditorKit) is used from Netbeans.

Attached are screenshots of SwingSet2 demo and Netbeans javadoc view to demonstrate the problem.

issue was initially reported against Netbeans at
http://www.netbeans.org/issues/show_bug.cgi?id=64944, see for details.