这段代码应该怎么样去理解了？？～

SCRIPT>
var roll_image = new Array;
var image_link = new Array ;
var small_img = new Array;

roll_image[0] = http://www.to8to.com/designer/v-1s108;
image_link[0] = http://www.to8to.com/designer/v-1s190;
small_img[0] =http://www.to8to.com/designer/v-1s272;

roll_image[1] = http://www.to8to.com/designer/v-1s282;
image_link[1] =http://www.to8to.com/designer/v-1s368;
small_img[1] = http://www.to8to.com/designer/v-2s653;

roll_image[2] = 'images/03.jpg';
image_link[2] = 'http://www.68design.net/';
small_img[2] = http://www.to8to.com/designer/v-2s662;

roll_image[3] = 'images/04.jpg';
image_link[3] = 'http://www.68design.net/';
small_img[3] = http://www.to8to.com/designer/v-2s654;

roll_image[4] = 'images/05.jpg';
image_link[4] = 'http://www.68design.net/';
small_img[4] = http://www.to8to.com/designer/v-2s314;

roll_image[5] = 'images/06.jpg';
image_link[5] = 'http://www.68design.net/';
small_img[5] = http://www.to8to.com/designer/v-1s382;

roll_image[6] = 'images/07.jpg';
image_link[6] = 'http://www.68design.net/';
small_img[6] = http://www.to8to.com/designer/v-2s138;

var cliImg = '';
var cliImgSrc = '';
var imgNo = Math.round(Math.random() * 7);

var interval = 3000;
var setTime = '';

function click_simg(ci, no){
 var pImg = document.all.bigimg;
 var pLink = document.all.imglink;

 if(cliImg == '') {
  cliImg = ci;
  cliImgSrc = ci.src;
  ci.src = small_img[no];
  imgNo=no;
  pImg.src =roll_image[no];
  pLink.href = image_link[no];
 } else if(cliImg != ci) {
  cliImg.src = cliImgSrc;
  cliImg = ci;
  cliImgSrc = ci.src;
  ci.src = small_img[no];
  imgNo=no;
  pImg.src =roll_image[no];
  pLink.href = image_link[no];
 }
 clearTimeout(setTime);
 setTime=setTimeout("rotate()",interval);
}

function rotate(){
 imgNo = (imgNo >= 6) ? 0 : imgNo+1;
 var ci = eval('document.all.num_img'+imgNo);

 document.all.bigimg.filters.blendTrans.apply();
 document.all.imglink.href=image_link[imgNo];
 document.all.bigimg.src=roll_image[imgNo];
 document.all.bigimg.filters.blendTrans.play();

 if(cliImg == '') {
  cliImg = ci;
  cliImgSrc = ci.src;
  ci.src = small_img[imgNo];
 } else if(cliImg != ci) {
  cliImg.src = cliImgSrc;
  cliImg = ci;
  cliImgSrc = ci.src;
  ci.src = small_img[imgNo];
 }

 setTime=setTimeout("rotate()",interval);
}

//-->
</SCRIPT>