I’m experiencing some strangeness on semi-transparent gradient background PNGs.
If you look at the attached image, you can see that bottom left corner of this treecard seems to have a darker shadow than any of the other borders on the card. There are 3 background images on a treecard (header, middle and footer). All 3 of these images have been saved in photoshop in exactly the same way using the "export for web" feature. I have not changed any of the settings on each of the saved images.
One other really strange thing is that changing the background-color to #fff will cause the shadow to lighten and match up with the other shadows. But changing the background-color to transparent or nothing will cause the background-image shadow to darken again. Strange, no?
Convert to sRGB (not selected)
Image Size: Bicubic smoother, Constrain Proportions
Proof Setup under View menu: Windows RGB