http://mozdev.i2p/en-US/docs/Web/CSS/cross-fade
The above could also have been written as: css cross-fade ( url ( white.png ) 0% , url ( black.png ) ) ; /* fully black */ cross-fade ( url ( white.png ) 25% , url ( black.png ) ) ; /* 25% white, 75% black */ cross-fade ( url ( white.png ) , url ( black.png ) ) ; /* 50% white, 50% black */ cross-fade ( url ( white.png ) 75% , url ( black.png ) ) ; /* 75% white, 25% black */ cross-fade ( url ( white.png ) 100% , url ( black.png ) ) ; /* fully...