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
It is indeed very strange if you saved all three exactly the same. If all your images are doing the same thing in the footer section then it would seem like a repetition. Look in the code to see if you are not repeating the image twice on top of itself.