Is there such a thing as transluscency? Can I create an image with a transluscent shadow, such that whatever lies behind me image in a web page -- such as a background image or color -- will actually show through the gradient of the shadow? This might be an impossibility as far as I know.

In other words, it seems like it's necessary to commit to a particular background for a "transparent" image, whether that background is black, orange, white, etc. But no matter what you do, there is always a definite, specific place where the exported image ends and the stuff around it begins.

Just to put it in concrete terms, if you export some text with a white shadow, it will never be possible to actually see through the outlying area of the shadow, once you export. The outlying area of the shadow is transluscent in the vector-based program, but can never be transluscent, strictly speaking, once you export, correct? If you export the image while it's on a white background, and then post it online on a white background, there will be the appearance of transluscency, but real transluscency is impossible to achieve. This is a non-trivial matter when trying to apply a "transparent" image with a shadow over top of a non-uniform background. For example, if you have a banner that is partly in white space and partly over top of a background image.