function setCookie(nom, valeur, expiration) {
  document.cookie = 
    nom + "=" + escape(valeur) 
    + ((expiration == null) ? "" : ("; expires=" + expiration.toGMTString()))
}

function getCookie(nom) {
var recherche = nom + "=";
  if (document.cookie.length > 0) {
    offset = document.cookie.indexOf(recherche);
    if (offset != -1) { 
      // si le cookie existe
      offset += recherche.length;
      // position du début
      fin = document.cookie.indexOf( ";", offset);
      // position de la fin
      if (fin == -1) {
        fin = document.cookie.length;
      }
      return unescape(document.cookie.substring(offset, fin));
    } else {
      return "";
    }    
  } else {
    return "";
  }
}


<!--
function getCookieVal (offset) {
          var endstr = document.cookie.indexOf (";", offset);
          if (endstr == -1)
                endstr = document.cookie.length;
          return unescape(document.cookie.substring(offset, endstr));
        }
function GetCookie (name) {
          var arg = name + "=";
          var alen = arg.length;
          var clen = document.cookie.length;
          var i = 0;
          while (i < clen) {
                var j = i + alen;
                if (document.cookie.substring(i, j) == arg)
                  return getCookieVal (j);
                i = document.cookie.indexOf(" ", i) + 1;
                if (i == 0) break;
          }
          return null;
        }
// -->