According to the W3C Recommendation for the CSS background shorthand, the values are [<'background-color'> || <'background-image'> || <'background-repeat'> || <'background-attachment'> || <'background-position'>] | inherit.
Following that recommendation, I write a declaration like this:
background: transparent url("/images/layout/sprite.png") repeat-y scroll right top;
When I inspect that element in Firebug, it lists the color part last, instead of first:
background: url("/images/layout/sprite.png") repeat-y scroll right top transparent;
Using it the Firebug way seems to work, but it doesn't follow the W3C Recommendation. I tried some Google searches, but I couldn't find any information on this. Is there some history that I am unaware of? Is it a Firebug bug?
http://www.w3.org/TR/CSS2/about.html#property-defs
A double bar (||) separates two or more options: one or more of them must occur, in any order.
So, the background values may be listed in any order.