<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://ваш сайт/'+diz+'.css">');    

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