I'd like to put a logo png onto of another coloured png. They both have transparent backgrounds. When I try this the images blend together. Curiously, in Photoshop the logo retains its opaque-ness - I put colours on the layers underneath it, another image, etc etc, the logo is still opaque.

I'd like to do it this way so I can rotate the background images.

How do I fix this?

[edit]I've cooked up an example image: http://i.imgur.com/XtoGn.png

The left is what I want to happen, the right is what happens on all browsers (I know the background isn't transparent but bear with me - they're both transparent pngs, with the background having a gradient layer mask). I've put the images like this

<div>
    <img id="backgroundImg" style="position: absolute; top: 0;" src="/Images/background.png" />
    <img id="logoImg" src="/Images/logo.png" />
</div>

I'm not entirely sure what blending mode I'm using in PS.