<span style="border-left:100px solid white;border-top:400px solid red;width:0px;position:absolute;top:10px;left:10px"></span>
<span style="border-left:99px solid;border-left-color:transparent !important;border-left-color:yellow;;border-top:396px solid white;width:0px;position:absolute;top:10px;left:12px;filter:progid:DXImageTransform.Microsoft.Chroma(color='yellow')"></span>
<span style="border-right:100px solid white;border-top:400px solid red;width:0px;position:absolute;top:10px;left:110px"></span>
<span style="border-right:98px solid;border-right-color:transparent !important;border-right-color:yellow;border-top:392px solid white;width:0px;position:absolute;top:10px;left:110px;filter:progid:DXImageTransform.Microsoft.Chroma(color='yellow')"></span>
這個實現實在是有點匪夷所思了。IE/FF/OPERA下面可用。在safari下面計算border的時候有多一個像素的誤差，因此這個坐標要做一些調整：
<span style="border-left:100px solid white;border-top:400px solid red;width:0px;position:absolute;top:10px;left:10px"></span>
<span style="border-left:99px solid;border-left-color:transparent !important;border-left-color:yellow;;border-top:396px solid white;width:0px;position:absolute;top:10px;left:12px;filter:progid:DXImageTransform.Microsoft.Chroma(color='yellow')"></span>
<span style="border-right:100px solid white;border-top:400px solid red;width:0px;position:absolute;top:10px;left:110px"></span>
<span style="border-right:98px solid;border-right-color:transparent !important;border-right-color:yellow;border-top:392px solid white;width:0px;position:absolute;top:10px;left:110px;filter:progid:DXImageTransform.Microsoft.Chroma(color='yellow')"></span>