get wikipedia source failed (urrlib2)

[shahargs at gmail.com]

Hi,
I'm trying to get wikipedia page source with urllib2:
    usock = urllib2.urlopen("http://en.wikipedia.org/wiki/
Albert_Einstein")
    data = usock.read();
    usock.close();
    return data
I got exception because HTTP 403 error. why? with my browser i can't
access it without any problem?

Thanks,
Shahar.