Short but sweet: "background-position" tends to be a compound kind of setting, with a separate value for x and y, but the single key. This means jQuery's default animation function can't smooth animate it, like it can't animate color transitions. But just like how there's a plugin to let you animate colors there's one for backgroundPosition as well. There's not much to it besides what the page says. I stuck copies of both on my "just in case the links go away" jquery file archive at http://kirkjerk.com/m/files/.