On the effect of negative value of margin

In this paper, we talk about the effect of negative margin, we will use the margin in CSS, but the margin is set to negative, it may not be very good processing, margin negative value is not hack,margin negative values follow the document flow If a negative value is used to cause an element to move upward, the associated element will also be shifted, and a negative margin will be well compatible with each browser.

1. There are two borders, there are different background colors, regardless of the height of the increase, the other side also become high

2. Realizing self-adapting