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When checking my webpage with your validator set for HTML 4.01 strict", it reported that "frameborder" is not a valid attribute. But according to the standard at http://www.w3.org/TR/html401/present/frames.html#h-16.5 "frameborder" is legal. I tried to work around the problem by using a "style" attribute instead, but the validator reports "style" is not a legal attribute either! Page I checked: http://www.hccfl.edu/pollock/AUnix1/Proj-A-Partition.htm (and used the http://validator.w3.org/check/referer?verbose=1 link at the page bottom.
There is no iframe element in HTML 4.01 Strict, thus the frameborder attribute for that element does not appear in the HTML 4.01 Strict DTD. As it isn't in the DTD, the validator correctly reports it as invalid. Iframes, and the problems that come with them, are the province of Transitional DTDs.