[mapserver-users] classitem and class values affect display of map?

[Patrick Stanistreet]

I have been working with the itasca demo trying to learn mapserver and gis.

I have simplified the demo.map file to a single layer which displays just
a  colored in state outline.  The layer is ctybdpy2.

I would have guessed that I could change the class value to another city 
but when
I do that the map does not display.  Going back to itasca work fine.

Perhaps a pointer to why this occurs , I would be glad to read any
further documentation or pickup a recommended book that would
explain what is going on here.