Let us repeat that. Two freakin' pixels tall. It takes a village to raise a child and it takes at least 9 pixels to render a font. Length units are therefore not recommended. Percentage units Percentage units, like length units and relative keywords, refer to the size of the parent element.
Nothing is sadder than the murder of a beautiful theory by a gang of ugly facts.
And some versions of Netscape 4 for Windows treat percentages as pixels. Lest we forget, good old IE3 drops the ball by sizing percentages relative to the user's default font size, rather than to the parent element. Not the 24px you intended. Too bad for you. Too bad for your visitor.