Your map has a custom coordinate system and you are sharing a map image layer that is configured with a WFS layer, WMS layer, or WCS capability.
Assign a different coordinate system to the map.
Hover over the analyzer message. Click the Options button that appears and click Change Coordinate Systems Properties. On the Map Properties dialog box, on the Coordinate Systems tab, change the Current XY system to a predefined coordinate system.
Open Geospatial Consortium (OGC) services—such as WMS, WFS, and WCS—rely on common EPSG codes to define supported coordinate systems. Learn more about EPSG codes.
If you customize the coordinate system for a map—for example, if you change the central meridian for a projected coordinate system—there is no corresponding EPSG code. In these cases, ArcGIS writes EPSG:0 or SRS:0 into the OGC service's capabilities file. You can still share the service, since the service will default to SRS:84 (WGS 1984). However, the custom coordinate system specified in the map will not be available to users of the service, since no common EPSG code exists for it. Learn more about specifying coordinate systems.