i'm searching for the best and performant way to animate some elements (with jquery or mootools). for example, if i have to move an element, it's better to:
Absolute position + margin manipulation can do a nice trick if you do not specify left/top values.
What trick?
The element with absolute position but no left/top will be rendered in the same position in which a static element would occur, while margin-left/margin-top will add to that position.
Overall, I appreciate you don't mention static position as an option — animating such element would cause unnecessary layout reflow, which is the main drawback of DOM/timeout animations.
Among the options you do consider, I think the most performant is the background option. But it has limited application, since you can move only graphic content. So I'd go for option #1.