What is RGBA? I'm glad you asked. As CSS3 becomes more widely supported RGBA will become one of those attributes that you just cant live without. Why? Well first it is just cool. Second it eliminates those semitransparent png slices you have to make to create a that glass or screen effect over backgrounds. How does it work? Simple "R"= Red "G"= Green "B"= Blue and the tricky one "A"= Alpha. Put that together and you get "background: rgba(22, 120, 10, .25);