Presenting stimuli before they are consciously processed might influence peoples opinions.
The idea of Subliminal Stimulation is to use text or images (or even sound) that presents a message that is presented quickly enough to be registered by the sensory organs and the first brain areas, but too fast to be consciously recognized. This is something you could use on your site when you're using a video message/ tutorial / promo to sell your company or product.
BIG note: This is really one for the category 'fine-tuning' or 'how far can you go', but I liked to mention it since there are many (ghost) stories about it's effect. I quote:
The near-consensus among research psychologists is that subliminal messages do not produce a powerful, enduring effect on behavior; and that laboratory research reveals little effect beyond a subtle, fleeting effect on thinking. For example, priming thirsty people with a subliminal word may, for a brief period of time, make a thirst-quenching beverage advertisement more persuasive.
From: Psychology Wikia: Subliminal stimulation