One of the most disturbing things I have found out from building Mapdex is the lack of proper projection information set for mapservices.  It turns out that about 56.5% of mapservices lack a projection or cannot be assumed to be geographic.  Only 31.3% of mapservices have a valid projection while 12.2% can be assumed geographic. 

What happens if you don't have a valid projection set?

• You cannot use your mapservice within ArcMap with other data layers outside of your projection;
• All of your data layers in your mapservice have to be in the same projection;
• You cannot publish your mapservice to the National Map or to GOS;
• Other groups cannot use the valuable data within your mapservice within their data and/or applications;
• Your mapservice cannot be searched spatially within Mapdex or other map search engines.

There is a nice article in ArcUser about georeferencing ArcIMS services.  I encourage you to check it out.

http://www.esri.com/news/arcuser/0205/files/georef_arcims.pdf

Cheers,

Jeremy