the data argument is form like belows:
a=1&b=2
this character is use urllib.urlencode concat together
use a dict
e.g.
dict={}
dict["a"]=1
dict["b"]=2
data=urllib.urlencode(dict)
if you already has a form like a=1&b=2
then your did not use the urllib.urlcode function
i was made a mistake when google some blog same how to use urllib2.urlopen() follow the urllib.urlencode way
in fact my data is alreay the well format