Accepting this, the rules of design, are based on traits of beauty that repeat themselves. They are based on experience of what works and what does not. Contrast Contrast, is one rule of design. In Buddhism, recommended is the golden middle way, the perfect combination of these contrasts. So applies to design.
Good design consists of contrasts in shape, size, colour and typography.
Think about this when planning your design. Colours When creating for the web, think about colours. All colors have emotions attached to them. These emotions can be evoked by displaying the according colours in the right manner. Briefly, these are the colors and the respective emotions they evoke.