Rudder

That cause weird looking, like in the following screenshot.

It seems that now, Gif can be transparent, and PNG dynamics (APNG - http://loadingapng.com/what_is_apng), we are not stopping the progess, see for transparent Gif http://ajaxload.info/

(for reference: http://stackoverflow.com/questions/7411029/where-can-i-find-a-decent-transparent-ajax-spinner)