import urllib2
import httplib
httplib.HTTP._http_vsn_str = 'HTTP/1.1'

uri = 'http://blogs.msdn.com/MainFeed.aspx'
# uri= 'http://www.cincomsmalltalk.com/BottomFeeder/index.html'

request = urllib2.Request(uri)
request.add_header("Accept-encoding", "gzip, deflate")
result = urllib2.urlopen(request)
headers = result.info()
etag = headers.getheader("ETag")
last_modified = headers.getheader("Last-Modified") 

print "Content-Encoding:", headers.get('Content-Encoding')

request = urllib2.Request(uri)
if etag: request.add_header("If-None-Match", etag)
if last_modified: request.add_header("If-Modified-Since", last_modified)
try:
  result = urllib2.urlopen(request)
  print "no Error"
except urllib2.HTTPError, error:
  print error