#out {
width: 609px;/*這里寬度為奇數，bug就出現了！！改成偶數就OK了*/
height: 300px;
position: relative;
background:#FF0000;
color:#FFF;
}
#inn {
width: 200px;
height: 250px;
position: absolute;
top: 0px;
right: 0px;
background:#000000;
}

<div id=“out”>
<div id=“inn”>此處為內部絕對定位的 DIV</div>
</div>