I did some research and found a very helpful blog post showing the how and the why of bookmark icons when using tablets and smartphones.
https://blog.zen.co.uk/setting-a-home-s ... d-devices/
In AbleCommerce, it's as simple as loading the PNG file in the root of the store. Then adding the two lines specified in the blog to the <head> section of your base.master files. You'll find two base.master files: one in /Layouts/ and one in /Layouts/Fixed/.
Enjoy!
