width alanını 1000px yapın ve altına overflow:hidden komutunu ekleyin.
#HCB3_SlideStart {
width: 1980px;
left: auto;
right: auto;
height: 485px;
position: relative;
z-index: 1;
overflow: hidden;
}
#HCB3_SlideStart .HCB3_SlideB { width:1980px; width: 1980px; height: 485px; overflow: auto; position: absolute; }
.HCB3_Slide img { width:1980px; height:485px; overflow:hidden;}
#HCB3_SlideStart .HCB3_SlideB ul { background-position: center top;
margin-top: 0;
margin-right: auto;
margin-left: auto;
background-attachment: fixed;width: 48500px; list-style: none; position: absolute; top: 0; left: 0; margin: 0; padding:0; }
#HCB3_SlideStart ul li { display: block; float: left; padding: 0; height: 485px; width: 1980px; margin: 0; position: relative; }
#HCB3_SlideStart a.back:hover { background-position:-5006px -32px;}
#thumbNav { position:absolute; bottom:5px; left:5px; height:20px; z-index:0;}
#thumbNav a { background:url(../images/controlsA.png) -20px 0; width:20px; height:20px; display:block; float:left; text-indent:-9999px; cursor:pointer}
#thumbNav a:hover ,#thumbNav a.cur { background-position:0 0}
#start-stop { display:none}
#HCB3_SlideStart .HCB3_SlideB ul ul { position: static; margin: 0; background: none; overflow: visible; width: auto; border: 0; }
#HCB3_SlideStart .HCB3_SlideB ul ul li { float: none; height: auto; width: auto; background: none; }<div class="HCB-KALIP">
<div id="HCB3_SlideStart"><div class="HCB3_SlideB"><ul>
<li><a href=""><div class="HCB3_Slide"><img src="header1.jpg" height="485" width="1980" border="0" /></div></a></li>
<li><a href=""><div class="HCB3_Slide"><img src="header2.jpg" height="485" width="1980" border="0" /></div></a></li>
<li><a href=""><div class="HCB3_Slide"><img src="header3.jpg" height="485" width="1980" border="0" /></div></a></li>
</ul></div> </div>
</div>