1. Turn on firebug or developer tool in the browser and go to console;
2. Open up reorderer standalone demo: http://build.fluidproject.org/infusion/standalone-demos/reorderer/html/table-tr.html
3. Drag and drop an item in the table;
4. This error is reported in the console:

"NetworkError: 404 Not Found - http://build.fluidproject.org/infusion/standalone-demos/reorderer/images/drop.gif"