How to solve the problem of margin collapse-CSS Tutorial-php.cn

How to solve the problem of margin collapse

清浅

Release： 2018-11-20 15:49:13

Original

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This article shares the problem of margin collapse and methods to solve margin collapse. It has certain reference value and I hope it will be helpful to everyone's study.

Margin is to set the outer margin of the element. Normally when setting the margin value, the parent element should be positioned relative to the browser, and the child element is positioned relative to the parent element. However, we often encounter situations where no matter how the value is set for margin There is no response. Today I will share with you the method to solve this problem.

html code

<div class="box1">
   <div class="box2"></div>
</div>

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css code

.box1{
	width:200px;
	height:200px;
	background-color:rgb(16,128,214);
	}
.box2{
        width:100px;
	height:100px;
        background-color:rgb(128,227,248);
}

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Rendering

Image 12.jpg

##When setting the margin-top value Change

When setting margin-top:100px for box1, box2 also sets margin-top:100px. Only the parent element is 100px downward relative to the browser, but the position of the child element relative to the parent element is not. Change

Image 15.jpg

But when the margin-top set for the child element: 150px is greater than the height of the parent box, the child element will no longer be positioned relative to the parent element but with Move the parent element down 150px relative to the browser positioning

Image 14.jpg

From the above content we can know what margin collapse is

margin collapse

Margin collapse occurs when the parent is positioned relative to the browser but the child is not positioned relative to the parent.

The child seems to have collapsed relative to the parent

The vertical margin of the parent-child nested elements. The parent-child elements are combined together. The two of them will take the largest

value

to solve the problem. The method of margin collapse

The essence is to trigger the box's bfc (block format context block-level formatting context) to change the rendering rules of the parent element

Method 1

position:absolute;

Set relative positioning

Solve the margin collapse problem by adding a relative positioning attribute to the parent element

Image 17.jpg

Method 2

display:inline-block;

Set to line block level element

Image 17.jpg

Method 3

float:left and float:right;

Use float to change the style

Image 17.jpg

Method 4

overflow:hidden

Partially hidden display of the overflow box

Image 18.jpg

Summary: the above That’s it for this article. I hope to be helpful.

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