123456789101112131415161718<!-- 第一种方法 -->class="box"class="boxcontent"class="border-arrow"<!-- 第二种方法 -->class="box"class="boxcontent"class="second-arrow"<!-- 第三种方法 -->class="box"class="boxcontent"class="third-arrow"class="third-arrow-inner"
1234567891011121314151617181920212223242526272829303132333435363738394041* {padding:0;margin:0;list-style:none;border:0;}/*第一种方法*/.box {width:200px;height:100px;margin:20px auto;position:relative;}.boxcontent {width:198px;height:98px;border:1px solid #ccc;}.border-arrow {width:0;height:0;font-size:0;line-height:0;position:absolute;left:10px;top:-16px;}.border-arrow em,.border-arrow ins {width:0;height:0;display:block;position:absolute;border:8px solid transparent;border-style:dashed dashed solid dashed;}.border-arrow em {border-bottom-color:#ccc;}.border-arrow ins {border-bottom-color:#fff;top:1px;
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