1) Open any page JSP or XHTML
2) Try to DnD external page or image from local place that doesn't belong to a project
ASSERT: Insert tag dialog with options appears
3) Choose any option and press OK
ASSERT: Empty tag is inserted

I don't think that it is a correct behavior in such situation. There many different variants exist to rebuild it: insert absolute path for required attribute, make a warning that current page or image doesn't belong to a project, or disable DnD from local space at all. We have to find a decision of this problem. I propose to insert absolute path for required attribute. Any other suggestions maybe?