Drop elements inside iframe only else revert
问题 EDIT:1 This is drag.html (main page) - <!doctype html> <html lang="en"> <head> <meta charset="utf-8" /> <title>jQuery UI Sortable - Handle empty lists</title> <link rel="stylesheet" href="http://code.jquery.com/ui/1.10.1/themes/base/jquery-ui.css" /> <script src="http://code.jquery.com/jquery-1.9.1.js"></script> <script src="http://code.jquery.com/ui/1.10.1/jquery-ui.js"></script> <link rel="stylesheet" href="http://jqueryui.com/resources/demos/style.css" /> <style> .drag {padding:10px;border