The test states:
Enter in the text field below with the pointing device or with the keyboard (with the tab key or with the "T" accesskey) and then enter some text into it. A message in green should then have appeared on its right-hand side indicating that such text field has received focus. In order to pass this test, the tester should not have to move the pointing device outside the text field.
IE8 Mode (All Versions)
The tab key does not give focus to the textarea element.
The test fails because the :focus pseudo-class does not match when followed by a combinator.
Section 2.2.12, V0194