margin: 0 auto; core changes the left and right of the box to auto

Width must be set

* { margin: 0; padding: 0; }

1. Merging of vertical margins of adjacent block elements

2. Merging vertical margins of nested block elements

The effect is the same when the angle is 90° and the side length of the angle is set.

Same as border

border-radius: 1px 1px 1px 20px;

border-radius: 10px 0;

Normal display method: one block-level element is displayed per line, and inline elements are displayed multiple times per line.

1. Floating inside the parent box will not exceed the range of the padding and border.

2. If one sub-box is floated, the rest of the sub-boxes should be floated.

3. Default implicit conversion of inline block elements

4. Floating affects the box below

1. Float first creates the concept (wrapper) of the containing block. That is, a floated element is always aligned with its nearest parent element. But it will not exceed the range of the padding.

2. For a child box inside a parent box, if one of the children is floated, the other children need to be floated. This will allow the display to be aligned in one line.

3. After adding float to an element, the element will have the characteristics of an inline block element. The size of the element depends entirely on the defined size or the default content float. The corresponding float is displayed based on the writing position of the element.

width > padding > margin