IE's massive font is by design, IIRC it used 12pt Verdana if it couldn't find a font tag (and font tags are deprecated in favour of CSS these days, so it falls back to its default font, not that MS followed W3C standards anyway *cough* MARQUEE *cough*).
I fell victim to IE's monopoly and custom extensions in the early 2000s with my Tekken website (which has since been inactive for many years, and was for a long time broken in Netscape, and later, Firefox and other modern browsers). In fact, the entire website was a hack job, character pages converted from Word 97 to HTML, briefly edited in FrontPage 4.0, then edited entirely in Notepad to remove FrontPage bloat. The pages don't even have a DOCTYPE declaration in the header!