Detailed explanation of examples of several tips in css-CSS Tutorial-php.cn

Detailed explanation of examples of several tips in css

黄舟

Release： 2017-08-03 15:43:05

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1.When the margin-top, margin-bottom and padding-top, padding-bottom of the element use percentage as the unit, they are relative to the width of the parent element. width, rather than height as we imagine; as shown in the figure

<style type="text/css">
        .parent{
            outline: 1px solid orange;
            width: 200px;
            height: 300px;
            padding: 10px;
            margin: 10px;
        }
        .child{
            outline: 1px solid purple;
            width: 200px;
            height: 80px;
            padding-top: 10%;    　　/*20px = 父容器的width值200px * 10% */
            padding-bottom: 5%;     /*10px = 200px * 5% */
            margin-top: 20%;    　　/*40px = 200px * 20%*/
            margin-bottom: 15%;    /*30px = 200px * 15%*/
        }<body>
    <p class="parent">
        <p class="child"></p>
    </p>
</body>

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The sub-box parameters are as follows:

2. Elements containing positioning attributes, their top and bottom units When it is a percentage, the percentage is relative to the height of the parent element. left and right are relative to the width of the parent element.

<span   style="max-width:90%">.parent{
            outline: 1px solid orange;
            width: 200px;
            height: 300px;
            padding: 0px;
            margin: 0px;
            position: relative;
        }
        .child{
            outline: 1px solid purple;
            width: 200px;
            height: 80px;
            position: absolute;
            top: 5%;　　/* 15px = 300px * 5% 上边框离父盒子上边框15px的距离*/
            left: 20%;　　/*　　40px = 200px * 20% 左边框离父盒子左边框40px的距离　　<br/>　　　　　　　　　　　　　　　　　　 也就是子盒子左上角的坐标为x=15,y=40（父盒子左上角为原点）  */ 
            
        }</span>

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3. Border width Cannot be expressed as a percentage

4.width:100%

4.1 When there is an absolutely positioned child element in the parent container, the child element is setwidth:100% Actually Refers to the width of padding+content relative to the parent container.

rAs shown in the figure:

<style type="text/css">
    .parent{
        outline: 1px solid orange;
        width: 200px;
        height: 300px;
        padding: 10px;
        margin: 10px;
        position: relative;
    }
    .child{
        outline: 1px solid purple;
        width: 100%;　　/* width = 220px = 父容器的padding+content*/
        height: 80px;
        position: absolute;
        top: 0;
        left: 0;
    }
</style>

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##4.2

When the child element is non-absolute When the element is positioned (it can be relative positioning), or if it is not positioned, width:100% refers to the content of the child element, which is equal to the content width of the parent element.

.parent{
    outline: 1px solid orange;
    width: 200px;
    height: 300px;
    padding: 10px;
    margin: 10px;
}
.child{
    outline: 1px solid purple;
    width: 100%;  /* width:200px = 父盒子的content*/
    height: 80px;
}

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.parent{
    outline: 1px solid orange;
    width: 200px;
    height: 300px;
    padding: 10px;
    margin: 10px;
    position: relative;
}
.child{
    outline: 1px solid purple;
    width: 100%; 
    height: 80px;
    position: relative;
}

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