Defines how overflowing content on both horizontal and vertical axis is displayed.
默认属性
overflow: visible;
The overflowing content is visible, while the element itself stays at the specified height.
overflow: hidden;
The overflowing content is hidden and can not be accessed.
overflow: scroll;
The overflowing content is accessible thanks to a vertical scrollbar.
overflow: auto;
The browser decides whether to display a vertical scrollbar or not.