Are semi-transparent images supported widely yet?

What are the implications of using this effect?

What can go wrong?

Are there alternatives?

Thanks

Are you referring to transparent PNGs ?

Yes.

I think so.

The only browser that I know of that does NOT support transparent PNGS on it's own is IE6 (and below). To make IE6 do it you need some bit of scripting and even then it's limited to non-repeating images.