Unfortunately, PNGs are still not universally supported, and thus you run the risk that some users will not be able to see inline PNGs. And even the browsers that do support PNGs don't fully support all the nifty, useful features.

Versions 4 and Up of the "Big Two" (except IE 4 for the Macintosh) can view PNG images but support for advanced features such as gamma correction and alpha transparency remain broken and buggy.

-- Rozallin J. Thompson
The Webmistress who doesn't hesitate to use strict;