The applet size is 800x500
You can place a point on the surface, so I created a 2D slider (purple point) in the graphics window. The axes on the 2D slider are oriented in the same was as the 3D view is originally.
With grid and perspective.
With grid and perspective, but no grey plane.
perspective, but no grey plane and no grid.
Grid on surface. Tried to edit in the applet and lost the slider. Lesson learned.