There is a gray icon on my home screen.
After turning restrictions off on my iPad a weird gray icon popped up on my home screen and I can't delete it.
iPad (3rd gen) Wi-Fi, iOS 6.1.3
Are you sure that it isn't a shortcut to a website? But you should be able to delete it by tapping and holding down on the icon until the X to delete pops up.
Can you post a screenshot of the icon?