背景图像悬停不在Colorbox模式中工作

Question

我正在尝试重新设置此灯箱插件（https://github.com/jackmoore/colorbox），但悬停在我的上一个和下一个按钮上的情况与我想要的其他图像无关。我已经花了好几个小时，没有太多运气。这是代码：

/* This is the image placed behind the previous and next buttons */
#cboxTopLeft{
width: 248px;
height: 91px;
background: url(images/projectnavbg.png) 0 0 no-repeat;
margin: 30px 20px -120px;
position: relative;
z-index: 1;
}

/* These are the buttons */
#cboxPrevious, #cboxNext {
border:0; 
padding:0; 
margin:0; 
overflow:visible; 
position:absolute;
text-indent:-9999px; 
z-index:1; 
width: 111px; 
height: 21px; 
bottom:375px;
}

#cboxPrevious:active, #cboxNext:active, #cboxSlideshow:active, #cboxClose:active {
outline:0;
}

#cboxPrevious{
left:30px; 
background: url(images/prevnextbtns.png) 0 0 no-repeat;
}

#cboxPrevious:hover{
background-position: 0px -25px;
}

#cboxNext{
left: 145px; 
background: url(images/prevnextbtns.png) 0 0 no-repeat; 
background-position: -115px 0px;
}

#cboxNext:hover{
left: 145px; 
background-position: -115px -25px;
}