There's no distinction between text/html/css when you're writing this kind of thing. A CSS selector is a CSS selector. What you really did is go from using div.rotator (a div with class rotator) to using #rotator (an element with id rotator.)
You didn't post your html so I'm assuming, but you probably changed class="rotator" to id="rotator". So you'll have to use #rotator in your JavaScript now (actually jQuery.)
Incidentally, the preceding "div" is unnecessary in this case. You could probably write .rotator and div#rotator just as well.
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