It is just a split second decision.
The eyes of people visiting your website send signals to the brain, and the brain makes choices:
Will they buy or be turned off for good?
Will they open it or delete it?
Will they opt-in or will they click away?
From your initial ad- and all the way through your complete sales funnel- your prospect's behavior is greatly influenced by the things that they see.
Keeping that in mind, it is...