I’m overlooking something obvious in using my sprites. I have an example at JSFiddle.
It is not displaying the sprite in the span and when I look at the element in Chrome, it is reporting an actual background position of 0px, 50%. The css is 0px, -31px.
Suggestions
You have to make the SPAN display as block and lose the comma between your background position settings as there should simply be a space:
http://jsfiddle.net/HJUg6/2/