We cannot use skins we created due to Weblg error on a macbook

We created a skin on skindex and uploaded to our minecraft.net account. But when we then uploaded it from our computer to the game, we got this error under the skins tab saying that our device doesn't support weblg. see screen shot. I have read a couple other resolved issues on this page of similar problems but I do not understand. Could you please help. We are on a Macbook. Thank you very much. 

Note: under "affects/Versions" I did not know what to pick so I just chose the first one. Sorry and thanks.