Eighteen, positioning mechanism

Positioning mechanism: (mainly for block-level elements)
There are two types:
1. (standard) document flow (arranged from top to bottom, without changing any layout and position in the middle, such as screenshots)
2. Off-standard flow: (depart from standard documents) There are two kinds of flow), namely float, position: absolute), which is called float, also known as the realization effect of position (let block-level elements realize from left to right, from top to bottom),
such as letting content 4 out of the document flow, The
document flow features that appear after content 2 :
1. Blank folding phenomenon (the carriage return in the editing area is displayed as a space)
2. The height is uneven, the bottom is aligned
3. Automatically wrap, one line is filled, and the line is written ( It does not mean that the browser fills up from left to right, it means that the current container is filled with one line and then wraps)