SVG fallbacks are all about making the web faster. Unfortunately a few holes have been found in some recently featured techniques that mean two downloads occur rather than just the one. If you use SVG and fall backs it is well worth reading this article.
The idea was based on Jake Archibald’s revisiting of the fact that browsers render theAn excerpt from SVG Fallbacks
<img>. It’s just a weird alias from the days of yore that can be exploited.