Q:

Is the soundcloud html5 widget iframe styleable via css? 

I'd like to use the html5 widget + it's api (http://developers.soundcloud.com/docs/html5-widget)
My question: can tha widget be styled via CSS?  FireBug shows style information, once the player is loaded, and I'm wondering, if it is possible to change those styles? 

A:

No, this isn't possible.  The widget is inserted into the page in an iframe and I don't think it's possible to change the styles inside an iframe from outside.  The only "styling" which is catered for is changing the colour of the buttons and waveform, via the "color" url parameter. 
For example, here's a user's sounds widget with pretty pink buttons and waveform highlights:
http://w.soundcloud.com/player/?url=http%3A%2F%2Fapi.soundcloud.com%2Fusers%2F2&show_artwork=true&show_comments=false&color=ff00ff&show_playcount=false&liking=false
Here's the url reformatted for legibility:
http://w.soundcloud.com/player/
? url=http%3A%2F%2Fapi.soundcloud.com%2Fusers%2F2
&show_artwork=true
&show_comments=false
&color=ff00ff    <-----
&show_playcount=false
&liking=false

