Using the CSS3 image () in the content can greatly enhance the ability of developers.

- Using fallbacks (if image does not support, then display next).
- Display, for example, first frame of GIF image.
- Fill element by solid color, if have width and height attribute.
- NOT JavaScript, pure CSS3.
- Images by CSS, not only HTML5.
- Visual custom elements (display canvas instead img, but this element is img).

Examples:

#img {
    content: image('cat_meme.gif#frame=5', 'lolcat.png');
}
Display 5'th frame of GIF image. Visual element is static.

#img:after {
    content: image('cat_meme.gif#frame=5', 'lolcat.png');
}
Insert to container 5'th frame of GIF image after content.

#img {
    content: element(#canvas);
}
Conversion simple image element to interactive canvas element. Size must correct working, like image element.

#img:after {
    content: element(#canvas);
}
Insert canvas element to after of content in container.