When working with a fixed width design, be sure to at least center the wrapper div to maintain a sense of balance (margin: 0 auto; usually does the trick).

如果要使用固定宽度设计，务必保证主容器居中对齐，以保持平衡(一般利用margin： 0 auto；就可以了)。

youdao

It may not be obvious, but the second and third layouts produce identical behaviors: They both maintain a fixed margin between the view and its superview as the superview's width changes.

或许不是很明显，但是第二第三个布局产生一样的行为：即使父视图的尺寸发生改变，它们都让视图和父视图的边距保持不变。

youdao

If there is no width constraint the view will stretch if you have a left and right margin.

如果没有宽度约束，如果您有左右边距，视图将伸展。

youdao