How come I coundn't drag one node from palette into diagram?

 There are one diagram and one pallette.  I tried to drag one node from  palette into the diagram, but as sonn as the dragged node  gets into the diagram above, it stays invisible.
 Pleast watch the red arrow to see what happened.  
 Any help is appreciated.

First, did you set Diagram.allowDrop to true in the target Diagram?

Second, I should mention that the Palette class inherits from the Diagram class. Every Diagram clips all of its drawing to be within the HTML DIV element that it is given.

So when the user starts a drag in a Palette, as long as the mouse/finger is inside the palette, whatever is being dragged is only drawn within the palette. When the mouse/finger moves into the other Diagram, whatever is being dragged will be drawn in that diagram. What is dragged may appear entirely differently due to different templates being used in different diagrams. See the behavior in GoJS Palette -- Northwoods Software.

Thanks walter, it’s really great help for me! everything is just perfect with your help!