<link id="dyncss" rel="stylesheet" type="text/css" href="">  
<script type="text/javascript">  
function setDynCSS(url) {  
if (!arguments.length) {  
url = (url = document.cookie.match(/\bdyncss=([^;]*)/)) && url[1];  
if (!url) return '';  
}  
document.getElementById('dyncss').href = url;  
var d = new Date();  
d.setFullYear(d.getFullYear() + 1);  
document.cookie = ['dyncss=', url, ';expires=', d.toGMTString(), ';path=/;'].join('');  
return url;  
}  
setDynCSS();  
</script>

<img style="cursor:pointer;" src="http://novofilms.ru/design/rega/2.png" onclick="setDynCSS('1.css')">  
<img style="cursor:pointer;" src="http://novofilms.ru/design/rega/1.png" onclick="setDynCSS('2.css')">