Re: An error pseudoselector for media

I wonder whether authors would want to be able to specify some generic fallback mechanism in CSS, like so:

  img[src^="file:"]:wont-load
    {content: url(path file attr(src), protocol "http", server "foo.example");}

  img[src$=".svg"]:wont-render
    {content: url(path name attr(src), extension "png");}

  file = name + (‘.’ + extension)?
  resource = path + (‘/’ + file)? + (‘?’ + query)? + (‘#’ + fragment)?
  …