How use urllib.urlopen()?

[Gustaf Liljegren]

Can't get the urlopen() function to work. I have a script on a UNIX web 
server that should go to another webpage when the user clicks a button. To 
isolate the problem, I made a test script:

#!/usr/local/bin/python

import urllib
u = urllib.urlopen("http://www.yahoo.com")
print u.read()

When running this I get HTTP 500 - Internal server error. :-( 

What's missing?

Gustaf