Re: handling fallback content for still images

I'm adding one more possible solution to the wiki: the CSS3 "content"
property.

While it is outside the scope of HTML, HTML 5 could recommend it for an
image with rich fallback content if it can be considered a viable solution.


Another "con" I failed to verbalize is that it ties the URL of the image -
which is often considered part of "content" - to CSS, which is
"presentation".  Using the "style" attribute to specify it helps with this.

Feel free to edit its pros and cons.