Bug
According to the CSS1 specification, released by the World Wide Web Consortium (W3C) in 1996 and revised in 1999, when a width or height is explicitly specified for any block-level element, it should determine only the width or height of the visible element, with the padding, borders, and margins applied afterward. Internet Explorer in "quirks mode" includes the content, padding and borders within a specified width or height; this results in a narrower or shorter rendering of a box than would result following the standard behavior.
Read more about this topic: Internet Explorer Box Model Bug