i would like to stop a drop if the drop is not "correct". The behavior schould be like an revert.

Like this:

drop: function() {
okay = ajaxtest($(this));
if (okay == false){
  Do something that the dragged element will be reverted;
}
}

i`ll be lucky, if someone can help me out. Btw, sorry for my bad english.
Greets Tavid