Combining images

How do I combine two images in a users' browser?

(PS, NOT the GD function that combines text onto an image, but two images, on on top of the other).

Thanks.

what exactly do you mean with combining? blending? placing them on top of each other?
IE has nice filter effects (but offcourse that's IE-only).
Placing them on top of each other is easy if you use CSS.

Got me excited now.
I dont understand CSS yet. I can do basic HTML, and I am getting on fine with PHP and MySQL. I haven't learnt CSS yet because there is only so much time in a day, on top of everything else.

One of my images has a regoin of transparency, and I want it to appear 'superimposed' on top of the other one.

I'd be grateful for a basic HTML/CSS example I can copy and paste, so I can see how its done. Maybe even two basic images, one with a region of transparency - Of course, when I learn how, I will be creating the images myself.

I don't know what you mean with superimposed, but this will make the one image appear on top of the other:

<div style="position:relative">
<img src="image_back.gif" style="display:block;position:absolute;top:0px;left:0px" alt="" />
<img src="image_top.gif" style="display:block;position:absolute;top:0px;left:0px" alt="" />
</div>