What are the layout methods of HTML web pages?

Summary of three HTML layout methods

1 Ordinary flow

Also known as regular flow , the default formatting method of the browser. Normal flow is how elements are rendered on a web page in most cases. All HTML is inside block boxes (block-level elements) or inline boxes (inline elements). When a browser begins rendering an HTML document, it allocates the space required by elements starting at the top of the window and working its way through the document's content. Unless the document's dimensions are specifically limited by CSS, the browser expands the document vertically to accommodate the entire content. Each new block-level element is rendered as a new line. Inline elements (inline element/inline block level) are rendered horizontally in order until the current line encounters a boundary, and then switch to the next line for vertical rendering.

2 Positioning flow

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absolute, absolute positioning: absolutely positioned elements The position is determined relative to the nearest positioned (positioning flow) ancestor (relative/absolute/fixed) element. If the element has no positioned ancestors, its position is relative to the initial containing block (body).

The position of the element is specified through the "left", "top", "right" and "bottom" attributes.

Absolutely positioned elements are out of standard flow. Does not take up space in the standard stream.

Absolutely positioned elements do not distinguish between block-level elements/inline elements/inline block-level elements.

If an absolutely positioned element uses the body as the reference point, then it actually uses the width and height of the first screen of the web page as the reference point, rather than the width and height of the entire web page. The positioned element will scroll as the page scrolls.

When a box is absolutely positioned, you cannot use margin: 0 auto; to center the box itself, you can use left: 50%; margin-left: - set the element width to half px to center;

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fixed, fixed positioning: Fixed positioning can be understood as a type of absolute positioning. Fixed positioning elements are positioned relative to the browser window. This enables the creation of elements that always appear at a fixed position in the window.

The position of the element is specified through the "left", "top", "right" and "bottom" attributes.

Fixed-positioned elements are separated from the standard flow and will not occupy space in the standard flow. That can be understood as being deleted from the standard stream.

Fixed positioned elements do not distinguish between block-level elements/inline elements/inline block-level elements.

E6 and lower versions do not support fixed positioning and can be solved using javascript.

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inherit, inheritance: inherit the value of the position attribute of the parent element.

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relative, Relative positioning: Relative positioning means moving relative to its previous position in the ordinary flow. That is, positioned relative to its normal position.

When using relative positioning, no matter whether the element is moved or not, the element still occupies the original space, so moving the element will cause it to cover other boxes.

In relative positioning, only one positioning attribute can be used in the same direction.

Relative positioning does not deviate from the standard flow, so distinguish block-level elements/inline elements/inline block-level elements in relative positioning. And because relatively positioned elements will occupy positions in the standard flow, setting attributes such as margin/padding for relatively positioned elements will affect the layout of the standard flow.

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static, static positioning: default value, no positioning, the element appears in the normal flow, that is, the normal flow above, ignoring top, bottom, left, right Or z-index declaration.

3 Floating flow

Floating flow has only one typesetting method, which is horizontal typesetting. It can only set an element to left or right alignment. The elements floated first will be displayed in the front, and the elements floated later will be displayed in the back.

There is no center alignment in the floating stream, and there is no center value. Margin: 0 auto cannot be used in floating streams.

In the floating stream, block-level elements/inline elements/inline block-level elements are not distinguished. Whether it is block-level elements/inline elements/inline block-level elements, they can be typeset horizontally. Both width and height can be set.

When an element is set to float, it will be separated from the standard stream (off-standard) and will not occupy space in the standard stream. If the following element is not floating at this time, then this element will cover the following element at this time.

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inherit, inheritance: inherit the value of the float attribute of the parent element.

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left, left floating: the element floats to the left. The one that floats first is on the left, and the one that floats later is on the right.

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none, not floating: default value.

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right, right float: the element floats to the right. The one that floats first is on the right, and the one that floats later is on the left.

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