1. WMS
GeoServer provides support for OGC Web Map Service version 1.1.1.
All the map preview functionality is built on top of the WMS protocol, just using different output formats.
For more information the about how to use the WMS protocol refer to the WMS specification (want something easier to digest? help us write a WMS tutorial 
).
You can also find more information and examples in the following articles:
Added by Jive, last edited by Andrea Aime on Dec 18, 2007
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