Logo che cambia ogni volta che si aggiorna la pagina

<script type="text/javascript"><!--
var ran=new Array();

ran[0]=("<style>.header{background-repeat:no-repeat;background-image:url('http://logo1.jpg')}<\/style>");

ran[1]=("<style>.header{background-repeat:no-repeat;background-image:url('http://logo2.jpg')}<\/style>");

ran[2]=("<style>.header{background-repeat:no-repeat;background-image:url('http://logo3.jpg')}<\/style>");

ran[3]=("<style>.header{background-repeat:no-repeat;background-image:url('http://logo.4.jpg')}<\/style>");

ran[4]=("<style>.header{background-repeat:no-repeat;background-image:url('http://logo5.jpg')}<\/style>")

var id=Math.round(Math.random()*(ran.length-1)); document.write(ran[id]);

//--></script>