var style_cookie_name = "style" ;
var style_cookie_duration = 30 ;

function switch_style(css_file)
{
var i, link_tag;

for (i = 0, link_tag = document.getElementsByTagName("link"); i < link_tag.length; i++)
  {
	if ((link_tag[i].rel.indexOf( "stylesheet" ) != -1) && link_tag[i].id) 
	{
		link_tag[i].disabled = true ;
		link_tag[i].href = "css/" + css_file;
		link_tag[i].disabled = false;
    }
  }
  
    createCookie(style_cookie_name, css_file, style_cookie_duration);
}

function set_style_from_cookie()
{
  var css_file = readCookie(style_cookie_name);
  
  if (css_file.length) {
    
	switch_style(css_file);
  }
}

function createCookie(name,value,days) {
	if (days) {
		var date = new Date();
		date.setTime(date.getTime()+(days*24*60*60*1000));
		var expires = "; expires="+date.toGMTString();
	}
	else var expires = "";
	document.cookie = name+"="+value+expires+"; path=/";
}

function readCookie(name) {
	var nameEQ = name + "=";
	var ca = document.cookie.split(';');
	for(var i=0;i < ca.length;i++) {
		var c = ca[i];
		while (c.charAt(0)==' ') c = c.substring(1,c.length);
		if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
	}
	return null;
}

function eraseCookie(name) {
	createCookie(name,"",-1);
}