I want to know if there is a code that I can use to change the layout of my site everyday, on it own. I know that there is a code to change the bg color for everyday of the week. Is this possible?

do a style sheet for each day or the week named like:
day0.css, day1.css, day2.css, etc

Then put this in the head of your pages:

<script type="text/javascript">
<!--
dt=new Date();
today=dt.getDay();
cssfile='day'+today+'.css';
document.write('<link rel="stylesheet" type="text/css" href="+cssfile+">';
//-->
</script>