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| <style>
div {
position: relative;
width: 300px;
height: 50px;
background-color: #bbb;
padding: 4px;
}
div:before {
content: "";
position: absolute;
left: 0;
top: -2px;
width: 50%;
height: 2px;
background-color: red;
}
</style>
<div>请看这个div的“上边框”是只有一半的</div>
|
