If I provide a default image to gravatar using the d parameter (for users who are not registered with gravatar), will gravatar redirect to the server hosting this default image or will it cache the image on it's server?
Example link: //gravatar.com/avatar/asdfs3rwerwesdfadsfas3/?d="mysite/img.jpg". Will gravatar cache img.jpg or does it redirect to mysite each time?
I looked up the response headers as suggested by @deceze in the comments. Gravatar hosts the image on it's domain (http://i*.wp.com/imagename). There is no redirect involved.