RGBA background colors are wonderful for creating a variety of effects, but I often wish I could apply a blur to an element in the stack, fuzzing out the elements below. This would be very similar to the glass effect on Windows Vista, or the "blur background" effect in iTerm on the Mac.
I suggest adding a new rule to support this:
opacity-blur: <blur radius>;
You can theoretically do with with SVG(XML) filters. Get the background image, apply a blur filter, then composite it before the source graphic. I have not examined to see if this actually works in webkit at the moment.
*** This bug has been marked as a duplicate of bug 68469 ***