Users visit websites and use apps to get things done, so emphasize the content of interest to communicate with your audience. Avoid design pollution that decorates the UI with non-communicative elements.

Users have learned to ignore content that resembles ads, is close to ads, or appears in locations traditionally dedicated to ads.

Summary: Design elements that appear similar in some way — sharing the same color, shape, or size — are perceived as related, while elements that appear dissimilar are perceived as belonging to separate groups.