Right now I am rebuilding a mobile website that will be catered to smartphones. I am trying to figure out the best way of serving up retina photos and I know the less images the better. Anyways, my question is I have most of them showing up as backgrounds within divs. I am using retina.js to swap the image for a higher res ones testing it on the iphone. Now at the bottom of the retinajs site it talks about using a less css mixin for backgrounds. I have tried to no avail to get this to work. I am also new to the less stylesheet so it could just be some type of configuration that I am missing which is why they aren't being swapped. It only works if I actually insert the image into the div. I have looked all over for simple steps from the beginning to no avail. I guess the instructions there are vauge to me.