I blogged about defining projections of your ArcIMS services and it looks like ESRI has posted an Instructional Series Podcast called “Best Practices: Defining Projection Information for ArcIMS Map Services”. Anyone who manages an ArcIMS implementation and hasn’t set their projections should listen to that podcast as your services will have trouble being consumed by ArcGIS Explorer and ArcMap clients without the projection being set. Direct link to podcast here.