@supports IE TestDrive Code Samples

block-filter.css

b {
	background-color: black;
	color: white;
}

@media only screen {
	b {
		background-color: white;
		color: black;
	}
}

rgba.css

b {
	background-color: black;
	color: white;
	background-color: rgba(255, 255, 255, 1);
	color: rgba(0, 0, 0, 1);
}

selector-filter.css

b {
	background-color: black;
	color: white;
}

b:only-child {
	background-color: white;
	color: black;
}

supports-filter.css

b {
	background-color: black;
	color: white;
}

@supports ( background: linear-gradient(0deg,white,white) ) {
	b {
		background: linear-gradient(0deg,white,white);
		color: black;
	}
}

http://dev.modern.ie/testdrive/demos/@supports/

This page refers to the rgba.css gist and mentions the rgba opacity value improperly.

All browsers will understand the background-color value “red”, but modern browsers that understand RGBa colors will apply a background color of green at 50% opacity as declared in “rgba(34, 132, 39, 0.5)”.