Brackground Positioning On a single Image

I have a sprite that is not behaving exactly the way it should. course01:hover is not positioning the background properly. Please help.

http://courses.stc.org


#course05 { height:85px; background-position:0 -392px; } /* Instructional Design */
#course05:hover { background-position:-421px -392px; }

I just made a small edit and specified the size of the last element. I had it working properly but once I made and edit to the image file I cannot get it to work the way it should. The gist is there’s a height issue for either the element or the image, and it does apply to all of them. This is my first attempt in making sprites. The edit I made is #course05:hover { height: 60px; }.

Looks OK to me in Firefox. Could you explain what “properly” is? Or what is going wrong? In what browser?