Getting Started with the Map Viewer : Using the map viewer : Using the Layer Manager : Reordering layers
  
Reordering layers
Using the Layer Manager, you can reorder layers that appear in the pane. If the layer is a grouped layer, the entire group can be moved to another position. You can also reorder layers within a group. However, you cannot remove a layer from the group.
NOTE: 
Reordering of layers can be done on layers that belong to REST-based map services and OGC.
Depending on the scale, these layers are displayed in the map viewer in the descending order of the layers as shown in the Layer Manager. For example, consider a scenario where you are viewing the Building and Parcels layers and you want to view the underlying Zones layer without the buildings and the parcels. You can move the Zones layer to a position above the Building layer and the Parcels layer. The following screen shows how layer reordering affects the visibility of layers in the map viewer.
Figure 20 
 
Figure 21