<script>     
function getCookie(c_name)     
{     
if (document.cookie.length>0)     
{     
c_start=document.cookie.indexOf(c_name + "=");     
if (c_start!=-1)     
{     
c_start=c_start + c_name.length+1;     
c_end=document.cookie.indexOf(";",c_start);     
if (c_end==-1) c_end=document.cookie.length;     
return unescape(document.cookie.substring(c_start,c_end));     
}     
}     
return "";     
}     

function setCookie(c_name,value,expiredays)     
{     
var exdate=new Date();     
exdate.setDate(exdate.getDate()+expiredays);     
document.cookie=c_name+ "=" +escape(value)+     
((expiredays==null) ? "" : ";expires="+exdate.toGMTString());     
}     

var diz = getCookie('mydiz') ? getCookie('mydiz') :'styles1';     
document.write('<link type="text/css" rel="StyleSheet" href="http://paint.3dn.ru/'+diz+'.css">');     

function dizsave() {     
setCookie('mydiz',document.getElementsByName('mdiz')[0].value, 365);     
location.reload();     
}     
</script>  

Выберите дизайн сайта:     
<select name="mdiz">     
<option value="styles1" selected="selected">Темный</option>     
<option value="styles2">Светлый</option>     
</select>     

<input type="button" name="save" onclick="dizsave(); return true;" value="Сохранить" />