首先搞个js的文件，如image.js，代码如下：
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("
");
for(i=1;i<=1;i++) {
myNum=(rand(3)); //改成你要随机显示的图片数；
if(myNum == 1) document.write("
"); //图片路径，可用http://
if(myNum == 2) document.write("
");
if(myNum == 3) document.write("
");
else {
document.write();
}
};
document.write("");
