localStorage object is undefined in IE

Try to open the file like this

file://127.0.0.1/c$/pathtofile/file.html

Are you testing this on a local HTML file? i.e. a file:/// URL?

localStorage is only available on HTTP websites. That hasn't changed in IE9 Dev Preview.

IE 11 WORKS

All you need two do add file://127.0.0.1 to the trusted zones under the security tab (NOTE: make sure https check box IS not checked) add this line to the top or your script, depending on your code you may not need to unless you get could not connect to the internet.

!localStorage && (l = location, p = l.pathname.replace(/(^..)(:)/, "$1$$"), (l.href = l.protocol + "//127.0.0.1" + p));

if (typeof(Storage) != "undefined") {
    // Store
    localStorage.setItem("lastname", "Smith");
    // Retrieve
    alert(localStorage.getItem("lastname"));
} else {
    alert("Sorry, your browser does not support Web Storage...");
}