I am using Facebook's Like button (https://developers.facebook.com/docs/reference/plugins/like/) but when displayed on Retina Display iPhone, the button looks blurry as the Facebook logo is an image and it is scaled up for high DPI. Is there any way to render the like button for Retina Display?
You'll need to overwrite Facebook's CSS.
First, create a new FB icon that is twice as big as the original you wish to replace (when scaled down, it will look good on retina).
Next, overwrite this this...
Here are a few additional options -> http://coding.smashingmagazine.com/2012/08/20/towards-retina-web/