The draggable global attribute is an enumerated attribute that indicates whether the element can be dragged, either with native browser behavior or the #HTML Drag and Drop API. #draggable can have the following values: true : the #element can be dragged. false : the element cannot be dragged.
If you apply draggable() to the modal dialog element, the browser window scroll bars will drag around the screen as you drag the modal dialog. The way to fix that is to apply draggable() to the modal-dialog class instead: $(". modal-dialog").