Does anyone know how to change opacity of MULTIPLE layers in Adobe ImageReady CS2? I have like 30 layers, and I'm trying to fade out effect of all 30 layers, if I do it manually I'll have to click layers and change opacity 300 times, that's ridiculous. When I select all layers for some reason the opacity tab is faded out?

Group them first, then you should be able to do it.

Ctrl G and then the option should be there for you.

Grouping a number of layers and changing the opacity of the group will not give the same result as changing the opacity of each layer.
Example: the top layer is 100% white and hides all layers below.
Option 1: Group, set opacity to 50%, result: 50% transparent white
Option 2: set opacity of each layer to 50%, result: each layer below is revealed (faded)

Workaround that comes to mind - if all layers are to have the same blending mode (e.g. Normal, 50% opacity)
- set one layer to the desired mode
- go to the Styles palette - New Style - name it appropriately (e.g. 50% transparent)
- select all layers, apply style (click on the new button at the end of the palette)

That sounds good!

if no animation is applied to individual layers while doing the fade out effect, you can also create a layer with a merged copy of all the layers.

Then just hide all the other layers and apply the fade out effect to the copy/merged layer

fade to black/white? if yes just put a black/white layer on top of everything and tween its opacity