Why does this validate?

From: Richard Savill (dreklind@btinternet.com)
Date: Fri, Sep 24 1999

Date: Fri, 24 Sep 1999 17:25:42 -0400 (EDT)
Message-ID: <002b01bf06d3$1ead4040$95e4abc3@default>
From: "Richard Savill" <dreklind@btinternet.com>
To: <www-validator@w3.org>
Subject: Why does this validate?

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<table summary="a_test_of_TD_width_att">
<td width="OK_buddy_I_want_50%_width">Test</td>


Below are the results of attempting to parse this document with an SGML

    No errors found!
 Congratulations, this document validates as HTML 4.0 Transitional!


Most obvious is that the parser doesn't recognise the 'blahblahblah' in the

Second, in any case, percentage is illegal according to even the
transitional DTD. I can't find where percentage is allowed here. Maybe I'm
reading it wrong.

Yet people use %, and render it in browsers. What's the deal here?

Richard Savill
The Jazz Age Page