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While creating and assigning map IDs is pretty simple for HTML5 and for WebHelp Pro, it happens that WebHelp Pro does not support HTML5 at this time.
So, you can create Multiscreen HTML5 or WebHelp Pro (for RoboHelp Server) output but they are mutually exclusive.
This help topic explains the creating and assigning map ID process
This explains what the application developer needs to do
This topic on Peter Grainge's site does a good job of explaining various alternative ways of calling help topics, even without using map IDs at all.
Adobe Certified RoboHelp and Captivate Instructor
Fortunately, you only have to set it once for all outputs. See this (old but topical) article by John Daigle: http://www.adobe.com/devnet-archive/robohelp/articles/context_help.html
Please post back if you have any other questions.