Imágenes que expiren cada determinado tiempo?

[famjaes]

</script>
<script language="JavaScript">
var imagenumber = 3;
var randomnumber = Math.random();
var rand1 = Math.round( (imagenumber-1) * randomnumber);

miFecha1 = 1;
miFechaF1 = 3;

images = new Array;
if(miFecha1 = mifechaF1)
images[0] = "";
else
images[0] = "../anuncios/FOTO1.png";
if(miFecha1 = mifechaF1)
images[1] = "";
else
images[1] = "../anuncios/FOTO2.png";
images[2] = "../anuncios/FOTO3.png";
links = new Array;
links[0] = "URL 1";
links[1] = "URL 2";
links[2] = "URL 3";

var image = images[rand1];
var link = links[rand1];



</script>