I have a map, and I want to overlay an image in such a way that I can fade the image from clear to opaque and back at will (like some weather sites do with radar information etc)
I started off thinking I needed to look at how the Z index can be messed with, but now I think I may be up the wrong creek.
Is this for a display, or going somewhere you won't have the convenience of having the thing in front of you to twiddle? 'Cos Photoshop'll let you do that.