Browsers have different default margins, for instance the p tag, h1 to h6 tags and the ul tag amongst others, so browsers interpret the standards differently. Some people state all margins and padding as 0 to begin with which will make all browsers the same, then add margins and padding as necessary.
However, a doctype does cure the worst problem where IE without a doctype calculates padding inside a div box dimensions, but outside like Firefox and others when a doctype is included.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.