is it possible (i think it is) to set limits to draggable items, like for example you can only drag a certain item farther than 1 half of the page?
yep there is. After you have the startdrag() script you should see two check able boxes. one says lock mouse to center and the other says bouding box. click that and type in the restrictions you want to put on your draggable object.
how do you determine the values for the limits?
just test it 