margin在所有元素上都可以设置(例如: div, span 等)
padding不能对行内元素生效(例如: span, img, a 等)
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<meta charset="UTF-8">
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<h5>padding 所有元素都可以设置</h5>
<div style="padding: 20px;">div</div>
<span style="padding: 20px;">span</span>
<h5>margin 行内元素(span,a,img等)不会生效</h5>
<div style="margin: 20px;">div</div>
<span style="margin: 20px">span</span>
<div style="display: flex;">
<span style="margin: 20px; width: 300px; height:300px; background:red;">span</span>
</div>
</body>
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