Publishing a map service
Once you finish creating your map, follow these steps to publish it as a map service:
Examine the report that appears at the bottom of your map. To publish a map service you need to resolve the items marked Error. However, you'll get the best performance and appearance if you resolve all the Warnings too. The Preview button can give you an idea of how your map will look, as well as the time you are gaining with each fix.
Tip: If you cannot resolve all the Errors, you can still publish a map service in Manager or ArcCatalog by browsing to the .mxd file. Performance will be slower if you publish the map service this way.
When you publish a map service using the Map Service Publishing toolbar in ArcMap, ArcGIS creates a map service definition (.msd) file that is placed in your server input directory. If you want to author the map on one machine and publish from a different machine, you can use the Save button on the Map Service Publishing toolbar to save the .msd file in a location you choose. You can transfer and publish this .msd file to any machine running ArcGIS Server that has access to your source map data.
If you edit your source .mxd after the service is running, you must save an updated .msd file, then restart the service in order for the changes to take effect.