Avoid pointless, extra design elements that unnecessarily increase cognitive load
In an August 2012 study by Google (PDF), researchers found that not only do users judge websites as beautiful or not within 1/50th to 1/20th of a second but also that ‘visually complex’ websites are consistently rated as less beautiful than their simpler counterparts.
In addition, ‘very prototypical’ websites—those with layouts commonly associated with websites in their category—with simple visual designs were consistently rated as most beautiful.
In other words, the simpler the design, the better.
Part of the reason that less ‘visually complex’ websites are considered more beautiful is that websites with less complexity don’t require as much work from the eyes and brain to decipher, retain, and process the information. The more color and light variations on the page (visual complexity), the more effort the eye has to put in to send information to the brain.
For this reason, it’s important to remember that every element—typography, logo, color choices, etc.—communicates subtle information about a brand. When these elements fail to do their job, webmasters often compensate by adding unnecessary text and/or images, which adds visual complexity and distracts from the overall aesthetic.
Optimizing a page for visual information processing—minimizing the amount of information that passes from the eye to the brain—is about communicating as much as possible with as few elements as possible.