The Form service is more or less obsolete; it really just gives an example of how to set up an HTML Form to invoke one of the STILTS commands using the Task Service.
The content served gives provides a couple of examples of an HTML form
that can invoke plotting using the Task Service.
The output graphics use the old-style plot commands
rather than the much more capable plot2*
plotting, and are not interactive;
for much improved server-side visualisastion,
see Section 11.1.