I expect one reason why the html police isn't going after the font size is that it isn't set in px, but in pt, so the browser scales the font differently depending on the screen's dpi.

Setting the font size in em's sounds utterly ludicrous to me, as the em is a unit sized relative to the current font size (normally the width of a lowercase "m").

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"God bless thee, my son; I will give thee the greatest jewel I have ...
"The end of our foundation is the knowledge of causes, and secret motions of things; and the enlarging of the bounds of human empire, to the effecting of all things possible."Trying to make sense of computers, The Error Log.