Decapentaplegic (DPP) exerts its long-range influence on wing patterning by acting 'directly' at a distance as a gradient morphogen, rather than 'indirectly' as a short-range inducer of other signals.
Major browsers support CSS3 gradients (including Internet Explorer 10), but with different rendering engines, it's still good to have fallbacks. Designing the presentation layer of an HTML5 ...