In the "Blending Layer Modes" tutorial it says to "have the paper layer selected, CTRL+click on the apple layer, CTRL+SHIFT+I and delete , in order to cut the paper that is out of the apple's shape" to sort of automatically cut one layer to the shape of another, but this doesn't do anything when i try it. what exactly is this command and is it a mistake? is there actually a way to cut one layer to the shape of another without doing it manually with an eraser or painting on a mask etc? thanks for any help you can offer! here's a link to the tutorial: http://photoshopcontest.com/tutorials/7/blending-layer-modes.html

CTRL clicking on a layer selects that layers shape.
then by going to another layer, Inverting the selection (right click/select inverse)
and hitting delete it deletes the stuff that isnt in the shape

You can clip the shape of one layer to that of a layer below it by using a clipping group. It is quite simple actually. You need only to Option/Click between the two layers. (Mac) I believe Alt/Click (PeeCee).

Anyway, you will see a funny looking cursor when you have the right key depressed and placed on the dividing line between two layers. Once they are clipped together the lower layers transparency acts as a mask for the layer above.

There are many very usefull things that can be done with this method of clipping layers together. One example is to use one layers blending mode to effect another.

Here is a simple example:

Create a curves correction layer over a background image (any image) and click ok to the curve layer without actually doing anything to the curve. Set its blending mode to lighten. Create another empty curve layer above the first and set its blend mode to overlay. Then clip the two curve layers together as above. The effect will be that the lighten mode will only allow the overlay mode to lighten the image and prevent the image from getting darker as would normally be the case with the overlay blend mode. Overlay is contrast blend mode that multiplys anything over 50% and screens everthing under 50%. By clipping it to another blend mode like darken or lighten you can split the control of the blend. This is very usefull and with a little imagination, I'm sure that you can think of many ways of using a blend mode to effect another blend mode in a similar fashion.

Here is a simplified tutorial by ReinMan.
http://photoshopcontest.com/tutorials/23/clipping-mask-101.html

thanks guys. good stuff.

mistake ? cant beeeeeeeeeeeeeeeeeee ;)

here there is a mistake in your title!!!
mistake in the "blending layer modes" tutorial? n ????

That was also written for an older version too, in CS2 you now have to control click on the layer thumbnail to make the selection, not just any part of the layer.