Less exact but IE6 compatible imitation of the localStorage object to provide localStorage in browsers that don't support it by using cookies.

localstorage-shim.js

// https://developer.mozilla.org/en-US/docs/Web/Guide/API/DOM/Storage#Compatibility

// Note: The maximum size of data that can be saved is severely
// restricted by the use of cookies. With this algorithm, use the
// functions localStorage.getItem(), localStorage.setItem(), and
// localStorage.removeItem() to get, add, change, or remove a key. The
// use of method localStorage.yourKey in order to get, set, or delete a
// key *is not permitted with this code*. You can also change its name
// and use it only to manage a document's cookies regardless of the
// localStorage object.
//
// Note: By changing the string
// "; expires=Tue, 19 Jan 2038 03:14:07 GMT; path=/" to: "; path=/"
// (and changing the object's name), this will become a sessionStorage
// polyfill rather than a localStorage polyfill. However, this
// implementation will share stored values across browser tabs and
// windows (and will only be cleared when all browser windows have been
// closed), while a fully-compliant sessionStorage implementation
// restricts stored values to the current browsing context only.


if (!window.localStorage) {
  window.localStorage = {
    getItem: function (sKey) {
      if (!sKey || !this.hasOwnProperty(sKey)) { return null; }
      return unescape(document.cookie.replace(new RegExp("(?:^|.*;\\s*)" + escape(sKey).replace(/[\-\.\+\*]/g, "\\$&") + "\\s*\\=\\s*((?:[^;](?!;))*[^;]?).*"), "$1"));
    },
    key: function (nKeyId) {
      return unescape(document.cookie.replace(/\s*\=(?:.(?!;))*$/, "").split(/\s*\=(?:[^;](?!;))*[^;]?;\s*/)[nKeyId]);
    },
    setItem: function (sKey, sValue) {
      if (!sKey) { return; }
      document.cookie = escape(sKey) + "=" + escape(sValue) + "; expires=Tue, 19 Jan 2038 03:14:07 GMT; path=/";
      this.length = document.cookie.match(/\=/g).length;
    },
    length: 0,
    removeItem: function (sKey) {
      if (!sKey || !this.hasOwnProperty(sKey)) { return; }
      document.cookie = escape(sKey) + "=; expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/";
      this.length--;
    },
    hasOwnProperty: function (sKey) {
      return (new RegExp("(?:^|;\\s*)" + escape(sKey).replace(/[\-\.\+\*]/g, "\\$&") + "\\s*\\=")).test(document.cookie);
    }
  };
  window.localStorage.length = (document.cookie.match(/\=/g) || window.localStorage).length;
}