Here is the CSS -

#slider ul, #slider li,
#slider2 ul, #slider2 li{
    margin:0;
    padding:0;
    list-style:none;

    }
#slider2{margin-top:1em;}
#slider li, #slider2 li{ 
    /* 
        define width and height of list item (slide)
        entire slider area will adjust according to the parameters provided here
    */ 
    width:500px;
    height:250px;
    overflow:hidden;

    }   
#prevBtn, #nextBtn,
#slider1next, #slider1prev{ 
    display:block;
    width:30px;
    height:77px;
    position:absolute;
    left:-30px;
    top:71px;
    z-index:1000;

    }   
#nextBtn, #slider1next{ 
    left:696px;
    }                                                       
#prevBtn a, #nextBtn a,
#slider1next a, #slider1prev a{  
    display:block;
    position:relative;
    width:30px;
    height:77px;
    background:url(../images/btn_prev.gif) no-repeat 0 0;   
    }   
#nextBtn a, #slider1next a{ 
    background:url(../images/btn_next.gif) no-repeat 0 0;   
    }   

/* numeric controls */  

#slider img{
width:500px;
height:300px;

}

ol#controls{
    margin:1em 0;
    padding:0;
    height:28px;    
    }
ol#controls li{
    margin:0 10px 0 0; 
    padding:0;
    float:left;
    list-style:none;
    height:28px;
    line-height:28px;
    }
ol#controls li a{
    float:left;
    height:28px;
    line-height:28px;
    border:1px solid #ccc;
    background:#b32d45;
    color:white;
    padding:0 10px;
    text-decoration:none;
    }
ol#controls li.current a{
    background:#5DC9E1;
    color:#fff;
    }
ol#controls li a:focus, #prevBtn a:focus, #nextBtn a:focus{outline:none;}

I want to center the #slider

HTML

<div id="slider">
<ul>
<li>IMAGE</li>
<li>IMAGE2</li>
</ul>
</div>