What is the difference between visibility:hidden and display:none?

Question

The CSS rules visibility:hidden and display:none both result in the element not being visible. Are these synonyms?

Answer 1

In addition to all other answers, there's an important difference for IE8: If you use display:none and try to get the element's width or height, IE8 returns 0 (while other browsers will return the actual sizes). IE8 returns correct width or height only for visibility:hidden.