The core method to achieve sticky heads or tails in web pages is to use the position: sticky property of CSS. 1. position: sticky is a combination of relative positioning and fixed positioning. It needs to be used in conjunction with top, bottom, left or right, and the parent container cannot have restricted attributes such as overflow: hidden or transform. 2. When making sticky footer, bottom: 0 is usually set and JavaScript or media queries may be required to control it not float when content is insufficient. 3. When using it, be careful to avoid parent container restrictions, reasonably set the z-index control hierarchy, ensure browser compatibility, and correctly handle layout conflicts between multiple sticky elements.

When making a web page, you may want certain elements such as the navigation bar or the bottom information to be displayed on the screen, no matter where the user scrolls. This is what is called "sticky" head or tail. It is actually not difficult to implement with CSS. The key is to understand how to use position: sticky and cooperate with other attributes.

1. Basic syntax and principles

position: sticky is the core of achieving sticky positioning. It's kind of like a combination of relative and fixed : when the element scrolls to a specific position, it "sticks" on the screen until it leaves the viewing area.

But a few things to note:

• It must be used with one of top , bottom , left or right , otherwise it will not take effect.
• The parent container cannot have properties such as overflow: hidden or transform that restrict its behavior.
• It only works when scrolling, not really pinned on the entire page.

For example, if you want a header to be fixed on the top when scrolling, you can write it like this:

 .header {
  position: sticky;
  top: 0;
}

As long as the page scrolls, the header will "stuck" when it reaches the top, and the page will not disappear even if it continues to scroll.

2. Tips for making sticky footer

Compared to the head, footer is a little more complicated to "stick" at the bottom. Because most of the time we want it to appear after the content, but not float when the content is not long enough, and start to fix it when the content is long enough.

A common practice is to judge the content height, and footer becomes sticky when it exceeds one screen:

 .footer {
  position: sticky;
  bottom: 0;
}

But this is not enough. Make sure the footer doesn't stick to the bottom of the screen at the beginning, and it's best to let it appear behind the content naturally. You can set its position to relative and switch to sticky dynamically via JavaScript, or use media query control.

Also, if you just want footer to always be at the bottom of the page (not when scrolling), it's better to use position: fixed , but this may block the content and require additional processing spacing.

3. Avoid common pitfalls

Although position: sticky is very convenient, it is easy to get stuck in actual use:

• Parent container restrictions : sticky will be invalid if the parent element uses overflow: hidden . At this time, you can consider adjusting the structure and moving the sticky element out of the container.
• z-index control level : multiple sticky elements may block each other, remember to set priority with z-index .
• Compatibility issues : Modern browsers support it, but if you are still maintaining old projects, you still have to check the compatibility.

To give a simple scenario: you are making a page with a scrolling table, and the header and operation buttons need sticky. At this time, the two sticky elements may be misaligned. You need to set their top values separately to ensure that they do not overlap.

The final reminder

The most important thing to implement sticky header or footer is to understand the behavioral boundaries of position: sticky . It doesn't completely get out of the document stream like fixed , but instead decides when to "stick" based on the scrolling context. Therefore, the layout structure and parent style will affect the effect.

Basically that's it. It doesn't seem complicated, but when it's really used in a project, the details are easily overlooked.

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