Useful modernizr style technique for detecting svg support. It puts an image in the page with a Base64 encoded data-uri SVG element. If that loads, it adds an svg class to the page.
The script then sets an SVG image as a background in the css using specificity to add a png fallback.
However, it doesn’t allow for SVG data uris in background images. Maybe I’m doing something wrong, but this doesn’t appear supported in Firefox. http://jsfiddle.net/daneastwell/XSjnx/1/