What is fixed positioning

Fixed positioning is a positioning method that keeps an element in a fixed position relative to the browser window. Even if the page is scrolled, it will not move. Fixed-positioned elements will break away from the document flow and always stay in the browser. A certain position of the window does not move, and its position does not change even if the user scrolls the page up or down. To use fixed positioning in CSS, you need to set the element's position attribute to fixed, and use the top, right, bottom, and left attributes to determine the element's position relative to the browser window.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Fixed positioning in CSS is a positioning method that keeps an element in a fixed position relative to the browser window so that it does not move even if the page is scrolled. Fixed-positioned elements will break away from the document flow and always stay in a certain position in the browser window. Their position will not change even if the user scrolls up and down the page.

Implementation process:
To use fixed positioning in CSS, you need to set the position attribute of the element to fixed, and use the top, right, bottom and left attributes to determine the position of the element relative to the browser window. These four attributes determine the position of the upper left corner of the element, that is, the upper left corner of the element always stays at the upper left corner of the browser window and will not change even if the page is scrolled.

For example, if you set the top attribute of an element to 10px and the left attribute to 20px, the element will always stay in the upper left corner of the browser window, 10px from the top of the page and 20px from the left side of the page. This element stays in the same position no matter how the user scrolls the page.

Features:

1. Detached from the document flow: Elements using fixed positioning will be detached from the document flow and will not affect the position of other elements. This means that fixedly positioned elements can be placed on top of other elements without affecting the layout of other elements.
2. Fixed position: Elements using fixed positioning will maintain a fixed position relative to the browser window and will not move even if the page is scrolled. This means that no matter how the user scrolls the page, the element will stay in the same position.
3. Overlap other content: Because fixedly positioned elements break out of the document flow and overlay other elements, they often overlap other content. This means that they can be placed on top of other elements on the page, unless z-index values ​​are set on other elements to change the stacking order of the elements.

Application scenarios:
Fixed positioning is usually used to create elements that are always visible, such as site navigation, advertising banners, special messages, etc. These elements usually need to be displayed within the visible area of ​​​​the user's browser window at all times so that the user can view and use them at any time. For example, many websites use fixed positioning to create elements such as navigation menus or back-to-top buttons that are always visible.

It’s important to note that excessive use of fixed positioning may destroy the layout and accessibility of the page. Therefore, the effects and implications need to be carefully considered when using fixed positioning.

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