Xara allows you to link to objects in another layer than the main current layer.
This is useful for a variety of reasons and could for example be used to cause a larger version of a photo to display when mousing or clicking on a small version (photo thumbnail). An example of this is Photo Popup 1 from the Photo Objects folder in the Designs Gallery.
To Link an object to a particular layer, initially open the Layer Gallery and add a new layer. The layer should be added above the existing MouseOff and MouseOver layers. Add the large version of the photo to the new layer. Next select an object from your main layer (MouseOff) which you wish to link to the new layer. Select Web Properties followed by the Link Tab. Select the radio button Popup layer and select the layer name you wish to link your object to. Preview/ export your web page and clicking on the object will cause the large photo in the new layer to display.