hallo
<script type="text/javascript">
var MaxPix=6;
var hintergr=Array();
var zufall=Math.round(5*Math.random()+1);
for(var i=1; i<MaxPix+1; i++){
hintergr[i]="bild"+i+".jpg";
//alert(hintergr[i]);
}
var writeOut="<body background=\""+hintergr[zufall]+"\" bgcolor=\"#FFFFFF\">";
alert(writeOut);
//document.write(writeOut)
</script>