Read more about 8 optical illlusions to improve your mockups at CreativeBloq.com
Mockups, themselves, are a lot like illusions. Ideally, in appearance they should be identical to real, working sites, even though the illusion is quickly dashed if a user tries to interact. Optical illusions are, more often than not, a product of a few quirks and phenomena of human sight. Luckily, this knowledge has been well documented by science — the science of Gestalt.
Source: CreativeBloq