<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3c.org/TR/html4/loose.dtd"> <html> <head> <script language="JavaScript"> function function1() { alert(document.compatMode); } </script> </head> <body> <button onclick ="function1();">CompatMode</button> </body> </html>