About using ArcGIS Online services in Web applications
You can add ArcGIS Online services as layers in your Web Mapping Applications. To access ArcGIS Online services, you can make a connection to the server using Manager. Advanced developers can also use the Web ADF controls or one of the ArcGIS Server Web development APIs to add ArcGIS Online services.
This help system explains how to connect to ArcGIS Online services while building a Web application in Manager. For help with making an ArcGIS Online services connection programmatically or through the Web ADF controls, see the ArcGIS Server Developer Help for your platform.
The Web Mapping Application below was created in Manager and uses an ArcGIS Online service.
Overlaying map caches in Web applications
Each ArcGIS Online service uses a cache of prerendered images to quickly display the map. Each image is called a tile. When designing your own map caches that will overlay ArcGIS Online services in a Web application, there are some special rules to follow about how you create your cache tiles.
If you will be using your own map caches to overlay ArcGIS Online services, or vice versa, be sure to read Overlaying your own caches with ArcGIS Online services in the .NET Web ADF.
Setting the primary map resource in your Web application
In .NET Web applications containing more than one map service, the primary map resource determines which service will supply the coordinate system and zoom levels of the map. You may have noticed that when you build a Web application in Manager, there is a drop-down menu labeled Use coordinate system of. The service you select here becomes the primary map resource. If you use Visual Studio to build your Web applications, the primary map resource is a property of the Map control.
In general, you should set the ArcGIS Online service as the primary map resource. The only appropriate scenario to set a different service as the primary map resource is if the service uses the same coordinate system as ArcGIS Online services and is cached at scales that correspond to a sequential subset of the ArcGIS Online service scales.