@felgallApr 14.2008 — #0in and 0cm also have the exact same size as well.
Of course 1px, 1pt, 1em, 1%, 1in and 1cm are all different sizes (unless you just happen to have your system configured so that two of them just happen to match) which is why you need to define the units since otherwise you have half the browsers assuming you meant attometres and the other half assuming you meant parsecs (except for IE which splits the difference and assumes pixels).