[tintin]

Also note that SVG logo's are rendered far better than a scaled down pixel version. I tried a lot of different reduction methods but the SVG version was always "sharper". Just include it in your image-tag: <img src="logo.svg" alt="my logo">

I think you can use a background image as fallback.

[justincormack]

I find it is easiest to use javascript to set fallbacks.