Somewhat related to this question.
Outline and border are pretty similar (although they do have their differences, as explained in the referenced question), but they use exactly the same properties/values in the opposite order. For example:
border: 1px solid black;
outline: black solid 1px;
To me, this seems to be a glaring inconsistency that should have been avoided. When using both borders and outlines, it is easy to mix up the order and write invalid CSS. Is there any known reason these two similar items have the same values written in the opposite order?
EDIT:
It seems (at least in IE8) that both can (sometimes) accept the values in either order and work fine, which makes it seem a bit stranger that the standard would be to write them in these different ways.