Hello, As noted in a web2 docstring: # Ancient versions of netscape and *current* versions of MSIE send # If-Modified-Since: Thu, 05 Aug2004 12:57:27 GMT; length=123 # which is blantantly RFC-violating and not documented anywhere While we wait for web2, the attached patch [1] against SVN trunk revision13528 makes twisted.web fix the issue the same way as twisted.web2. ciao ste [1] http://twistedmatrix.com/bugs/issue976