This does not work in Firefox 22:
background-image: -moz-radial-gradient(48% -42%, 138px 138px, green 0%, lightblue 100%);
But it works in Chrome:
background-image: -webkit-radial-gradient(48% -42%, 138px 138px, green 0%, lightblue 100%);
It's the second argument Firefox has a problem with. If changed to
background-image: -moz-radial-gradient(center, ellipse cover, #008000 0%, #add8e6 100%); /* FF3.6+ */
it works in FF, but that was not really the effect I'm after!