请问谁那有"每刷新次网页时可以改变图片"的代码??????????

<script language="JavaScript">
<!--
today=new Date();
jran=today.getTime();
function rnd() {
ia=9301;
ic=49297;
im=233280;
jran = (jran*ia+ic) % im;
return jran/(im*1.0);
};
function rand(number) {
return Math.ceil(rnd()*number);
};
document.write("<CENTER>");
for(i=1;i<=1;i++) {
myNum=(rand(18));
if(myNum == 1) document.write("<img src='/images/sj/1.jpg'>");
if(myNum == 2) document.write("<img src='/images/sj/2.jpg'>");
if(myNum == 3) document.write("<img src='/images/sj/3.jpg'>");
if(myNum == 4) document.write("<img src='/images/sj/4.jpg'>");
if(myNum == 5) document.write("<img src='/images/sj/5.jpg'>");
if(myNum == 6) document.write("<img src='/images/sj/6.jpg'>&quo