Positioning

The position property in CSS is a commonly used element positioning solution. The commonly used values for position are static, relative, absolute, fixed, sticky, and inherit.

static

The static property is the default value for HTML elements, which means there is no positioning. It follows the normal document flow and ignores the settings for the top, bottom, left, right, and z-index properties.
Document flow refers to the process of arranging box elements in a flow from left to right and top to bottom.
Text flow refers to the process of arranging text elements in a flow from left to right and top to bottom.
Taking an element out of the document flow means removing it from the normal layout arrangement. When positioning other boxes, the element that is taken out of the document flow is considered non-existent.

<div class="t1">static</div>
<style type="text/css">
    div{
        border: 1px solid #eee;
    }
    .t1{
        position: static;
    }
</style>

relative

relative is relative positioning, where the element's position is offset relative to its original position. It does not take the element out of the document flow. It works with the top, bottom, left, right, and z-index properties. When offset properties are set, the relatively positioned element will move accordingly, but its original space will not change. Relatively positioned elements are often used as container blocks for absolutely positioned elements.

<div class="t2">relative</div>
<div>Compare the effect. The element's original space remains unchanged, but there is an offset with relative positioning.</div>
<style type="text/css">
    div{
        border: 1px solid #eee;
    }
    .t2{
        position: relative;
        bottom: -10px;
    }
</style>

absolute

absolute is absolute positioning, where the element's position is relative to its nearest positioned ancestor. If the element does not have a positioned ancestor, then its position is relative to the <html> element. The usual approach is to nest a layer of relative positioned element as the parent element, and then set the offset of the absolutely positioned element relative to the outer relative element. Absolute positioning completely takes the element out of the document flow and text flow, and does not occupy any document space. It works with the top, bottom, left, right, and z-index properties.

<div class="t3">
    <div class="t4">absolute</div>
</div>
<style type="text/css">
    div{
        border: 1px solid #eee;
    }
    .t3{
        height: 300px;
        position: relative;
    }
    .t4{
        position: absolute;
        top: 100px;
    }
</style>

fixed

fixed is a positioning property that fixes the element's position relative to the browser window. Even if the window is scrolled, the element will not move. Note that when using fixed within an <iframe>, the element is positioned relative to the <iframe>. An <iframe> is like creating a new browser window within the page. fixed positioning completely removes the element from the document flow and does not occupy any document space. The top, bottom, left, right, and z-index properties are effective for fixed positioning.

<div class="t5">fixed</div>
<style type="text/css">
    div{
        border: 1px solid #eee;
    }
    .t5{
        position: fixed;
        top: 300px;
    }
</style>

sticky

sticky is a positioning property that positions the element based on the user's scroll position. The position of the sticky element depends on the user's scroll. It switches between position: relative and position: fixed. When the page is displayed, sticky behaves like position: relative, but when the page is scrolled beyond the target area, sticky behaves like position: fixed. It will stick to the target position. The element's positioning behaves as relative positioning until it crosses a specific threshold, and then it becomes fixed positioning. This specific threshold refers to one of top, right, bottom, or left. sticky positioning only takes effect when one of these four threshold values is specified. Otherwise, its behavior is the same as relative positioning.

<div class="t6">sticky</div>
<style type="text/css">
    div{
        border: 1px solid #eee;
    }
    .t6{
        position: sticky;
        top: 0;
    }
</style>

inherit

inherit positions the element based on the inherited position value of its parent element.

<div class="t7">
    <div class="t8">inherit</div>
</div>
<style type="text/css">
    div{
        border: 1px solid #eee;
    }
    .t7{
        position: relative;
    }
    .t8{
        position: inherit;
        bottom: -10px;
    }
</style>

Code Example

<!DOCTYPE html>
<html>
<head>
    <title>position</title>
    <style type="text/css">
        div{
            border: 1px solid #eee;
            margin: 5px 0;
        }
        .t1{
            position: static;
        }
        .t2{
            position: relative;
            bottom: -10px;
        }
        .t3{
            height: 300px;
            position: relative;
        }
        .t4{
            position: absolute;
            top: 100px;
        }
        .t5{
            position: fixed;
            top: 300px;
        }
        .t6{
            position: sticky;
            top: 0;
        }
        .t7{
            position: relative;
        }
        .t8{
            position: inherit;
            bottom: -10px;
        }
    </style>
</head>
<body>
    <div class="t1">static</div>
    <div class="t2">relative</div>
    <div>Compare and observe the effects. The element originally occupies the same space, but relative positioning will cause offset.</div>
    <div class="t3">
        <div class="t4">absolute</div>
    </div>
    <div class="t5">fixed</div>
    <div class="t6">sticky</div>
    <div class="t7">
        <div class="t8">inherit</div>
    </div>
    <div style="height: 1000px">Make the browser display a scroll bar</div>
</body>
</html>

Daily Question

https://github.com/WindrunnerMax/EveryDay

References

https://www.zhihu.com/question/21911352 https://www.runoob.com/css/css-positioning.html https://developer.mozilla.org/zh-CN/docs/Learn/CSS/CSS_layout/Normal_Flow
ON THIS PAGE