a[download] demo browser support should be updated

https://github.com/ebidel/html5demos/blob/master/html5-demos.appspot.com/static/a.download.html

Line 256 should be updated:
<code>&lt;p>&lt;b>Browser support&lt;/b>: right now, only Chrome dev channel (14.0.835.15+) supports this attribute.&lt;/p></code>

The download attribute now works in Chrome stable channel, Firefox and Opera (and maybe more).