changing or assigning Safari ios7 favorite icons on safari home screen

Does anyone have any idea how to do this? the home screen is my bookmarks folder (by default), and there are icons for each website, but the icons are generic and some are just blank. does anyone know how to manaually assign them or force update them?

any help would be great

Details:

Using Ios 7.0.3

Bookmarks synced via icloud to a pc and ipad (same problem on ipad)