<style>.x{width: 500px;height:1000px;background: yellow;position: relative;}.y1{width: 100px;height: 100px;top:100px;position: relative;background: red;}.y2{width: 100px;height: 100px;top:0px;position: relative;background: green;}</style><div class="x">    <div class="y1">    </div>    <div class="y2">    </div></div>上述代碼的結(jié)果如下圖所示，我在相對(duì)定位中使用top，當(dāng)top=0px時(shí)，為什么.y2完全蓋住了.y1，我用的可是相對(duì)定位??？謝謝