<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>WAI_2_3_5</title></head> </style> <body> <!-- the following elements should raise errors --> <h1>header 1</h1> <h2>header 2</h2> <h4>header 4</h4> <h2>header 2</h2> <h5>header 5</h5> <!-- the following elements should be fine --> <h6>header 6</h6> </body> </html>