<!doctype html><style>
* {
padding: 0;
}
html {
background: white;
}
body {
background: pink;
}
.not-bfc {
margin-top: 30px;
height: 20px;
background: orange;
}
.bfc {
margin-top: 30px;
display: flow-root;
}
</style><div class="not-bfc"></div><div class=bfc></div><div class="not-bfc"></div>