This is really cool, great work!<p>The only problem I can see is that it doesn't work with sites that use user agent sniffing serve up mobile sites (see bbc.co.uk - <a href="http://dfcb.github.com/Responsivator/?site=bbc.co.uk" rel="nofollow">http://dfcb.github.com/Responsivator/?site=bbc.co.uk</a>) I realise that's not technically 'responsive', but it would be cool if responsivator could handle that as well.<p>Having said all that, I don't think it's even possible to spoof different user agents in iframes(?), maybe could be done using a headless browser to take screenshots?