CSS: BFM
BFC:
block formatting context
"en"> "UTF-8"> "X-UA-Compatible" content="IE=edge"> "viewport" content="width=device-width, initial-scale=1.0">Document class="container">class="cube">
"en"> "UTF-8"> "X-UA-Compatible" content="IE=edge"> "viewport" content="width=device-width, initial-scale=1.0">Document class="float">class="normal">
"en"> "UTF-8"> "X-UA-Compatible" content="IE=edge"> "viewport" content="width=device-width, initial-scale=1.0">Document BFC
class="container">"bb.png" alt="">
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外边距塌陷 可给父元素border-top
"en"> "UTF-8"> "X-UA-Compatible" content="IE=edge"> "viewport" content="width=device-width, initial-scale=1.0">Document class="box">
内容塌陷
"en"> "UTF-8"> "X-UA-Compatible" content="IE=edge"> "viewport" content="width=device-width, initial-scale=1.0">Document class="box">