html – 已固定位置在Chrome中不起作用

我得到的问题是在Chrome中,箭头不会保持固定,当我向下滚动页面箭头随页面上升而你再也看不到它们了.奇怪的是,在Firefox中他们的工作并保持在最高位置：45％的位置：他们应该像往常一样固定.
以下是ff：https://www.dropbox.com/s/2vsrv874c3urlqs/firefox.PNG中如何工作的截图

这是铬：https://www.dropbox.com/s/zgr2zhkcnohykgj/chrome.PNG

箭头的html：

<div class="overlay-arrows">
        <div class="front-arrow-wrapper">
            <a href="#" rel="prev" class="prev-link">
                <div class="prev-icon">
                </div>
                <div class="prev-overlay">
                    <span class="categ-next">Category for prev</span>
                    <p>Title of the post for prev</p>
                </div>          
            </a>
            <a href="#" rel="next" class="next-link" >
                <div class="next-icon">
                </div>
                <div class="next-overlay">
                    <span class="categ-next">Category for next</span>
                    <p>Title of the post for next</p>
                </div>              
            </a>
        </div> <!--end .front-arrow-wrapper -->
    </div> <!--end overlay-arrows -->

和CSS：

.overlay-arrows{
    position: fixed;
    top: 45%;
    left: 0;
    width: 100%;
    z-index: 9999;
    overflow: visible;
}
.front-arrow-wrapper{
width: 1104px;
position: relative;
margin: 0 auto;
}
.prev-link{
left: 0;
float: left;
text-decoration: none;
}
.next-link{
right: 0;
float: right;
text-decoration: none;
}   
.prev-icon{
  background: url(../img/prev.png) 100% 0 no-repeat;
  height: 77px;
  width: 45px;
float: left;
}
.next-icon{
  background: url(../img/next.png) 100% 0 no-repeat;
  height: 77px;
float: right;
  width: 45px;
}
.next-overlay,.prev-overlay{
opacity: 0;
filter: alpha(opacity=0);
width: 250px;
width: 250px;
height: 77px;
color: #F16C14;
background: rgba(0,0.7);
font-size: 14px;
font-family: Helvetica,Arial,"Lucida Grande",sans-serif;
}   
.next-link:hover>.next-icon{
-webkit-transition: all 0.2s ease-out;
  -moz-transition: all 0.2s ease-out;
  -o-transition: all 0.2s ease-out;
  transition: all 0.2s ease-out;
  background: url(../img/next-hover.png) 100% 0 no-repeat;
}
.next-link:hover>.next-overlay{
  -webkit-transition: all 0.2s ease-out;
  -moz-transition: all 0.2s ease-out;
  -o-transition: all 0.2s ease-out;
  transition: all 0.2s ease-out;
  opacity: 10;
  filter: alpha(opacity=100);
}