The <font size=...> tags are only in the top navigation bar and is not the cause of the increasing text size. The increasing text is due to nested <h3> elements

The <font size=...> tags are only in the top navigation bar and is not the cause of the increasing text size. The increasing text is due to nested <h3> elements, where h3 is defined to have a relative size. If a font tag automatically closed a previous font tag, then you couldn't have nested font styles (e.g giving a word a different color than the containing text). But this have always been possible, otherwise the font element would be next to useless.