function accessibilita(css_files){ /* -------- css_files -> {'skin':'path of css file', .....} ----------- */
    
    var createCookie = function(name,value,days) {
      if (days) {
        var date = new Date();
        date.setTime(date.getTime()+(days*24*60*60*1000));
        var expires = '; expires='+date.toGMTString();
      }  else expires = '';
      document.cookie = name+'='+value+expires+'; path=/';
    };
    var readCookie = function(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);
      };
    };
    var removeCss = function () {
      $('link[type=\"text/css\"]').remove();
      $(document).ready(function(){
        $('style').remove();
        $('*').removeAttr('style');
      });
    };
    var setCss = function (path_file_css){
      $('head').append('<link href=\"' + path_file_css + '\" media=\"screen\" type=\"text/css\" rel=\"stylesheet\">');
    };    
    var setSize = function(size){
      var body = document.getElementsByTagName('body')[0];
      var percentuale = '75%'; // default
      if (size == 1) percentuale = '75%';
      if (size == 2) percentuale = '80%';
      if (size == 3) percentuale = '110%';
      body.style.fontSize = percentuale;    
    }
    this.setCookies = function (css_utente) { 
      createCookie('skinUtente',css_utente,365);
      location.reload();
    };
    this.setFontSize = function (size) {
      setSize(size);
      createCookie('fontUtente',size,365);
    };
    this.switchSkin = function(){
      var size = readCookie('fontUtente');
      if(size){
        setSize(size);
      };
      var skinUtente = readCookie('skinUtente');
      if(skinUtente){
        if (skinUtente =='grafica'){
          if(css_files[skinUtente]){
            setCss(css_files[skinUtente]);
          };
        }else {
            removeCss();
            if(css_files[skinUtente]){
              setCss(css_files[skinUtente]);
            };
            if(size){
             setSize(size);
            };
        };
      };   
    };
};