I agree with Anayar and The Zoq2, you can't view other people's fpm maps unless they are made up entirely of just stock segments and entities, or you just happen to have exactly the same custom media, in exactly the same folders.
The thread that The Zoq2 mentioned can be found here;
http://forum.thegamecreators.com/?m=forum_view&t=150383&b=25
This thread makes far more sense, as it does exactly what you're wanting; it shows other people the layout of your levels, so that they can 'see how a level should be' as you put it.