when the group is linked or a grey icon 
when the group is not linked. Use layer linking to have layers move together on the image canvas when you move one layer with the Move tool. To link individual layers, use the Layer Link button on the Layers palette. By default, this button says None. Change each layer that you want to link to the same number, say 1 or 2. Left-click to increase the number; right-click to decrease it.
Use group linking to have all layers within a layer group move together
on the image canvas. The Group Link button on the Layers palette displays
a blue icon when the group is linked or a grey icon when the group is not linked.
Layer links take precedence over group links. For example, Layer Group 1 is linked and contains Layer1, Layer2, and Layer3. Layer1 is set to link number 1. Layer4 (outside of the layer group) is also set to link number 1. If you move Layer4, Layer1 will move. If you move Layer2, Layer1 will not move.
To link layers:
For each layer you want to link, change its link set number to the same number. Do either of the following on the Layers palette:
Left-click the Layer
Link button 
to increase the number. Right-click the
Layer Link button to decrease the number.
Double-click each layer name to display the Layer Properties dialog, change the Link Set number, and then click OK.
To unlink layers:
For each layer you want to remove from the link set, do either of the following on the Layers palette:
Left-click or right-click the Layer Link button until it displays None.
Double-click the layer name to display the Layer Properties dialog, change the Link Set number to 0, and then click OK.
To link or unlink layer groups:
Do either of the following on the Layers palette:
Click the Group
Link button 
. A grey button means the group is unlinked.
Double-click the layer name to display the Layer Properties dialog, mark or clear the Group is Linked check box, and then click OK.
Changing the Opacity of Layers