Do you just love using rgba for backgrounds in CSS, but hate to make decent fallbacks for non-supportive browsers?
rgbapng is a Compass plugin for providing cross-browser* compatible RGBA support. It works by creating single pixel alpha-transparent PNGs on the fly for browsers that don't support RGBA. It uses the pure Ruby ChunkyPNG library resulting in hassle-free installation and deployment.
Install the gem:
gem install compass-rgbapng
Use the mixin to get a nice png fallback:
@include rgba-background( rgba(0,0,0,.75) );
background: rgba(0, 0, 0, 0.75);