1 <div style="width: 1200px;height:900px;margin: 0 auto;border: 1px solid #22DD22;">
 2     <div class="margin"></div>
 3     <div class="margin"></div>
 4     <div class="margin"></div>
 5     <div class="margin"></div>
 6     <div class="margin"></div>
 7     <div class="margin"></div>
 8     <div class="margin"></div>
 9     <div class="margin"></div>
10 </div>

 1 .margin {
 2     position: relative;       //使用定位是為了使用z-index，提高層級         
 3     width: 200px;
 4     height: 400px;                    
 5     border: 1px solid #000000;
 6     margin-left: -1px;       //邊框覆蓋，只顯示一個邊框
 7     margin-top: -1px;
 8     float: left;
 9 }
10 .margin:hover {
11     border-color: #22DD22;
12     z-index: 99;
13 }