Yo, the response headers set in ZPublisher.HTTPResponse our not always RFC compliant. In case of exceptions you get: (round lines 670 in HTTPResponse.py) if ev.find( '<html>') >= 0: ev = 'bobo exception' self.setHeader('bobo-exception-value', ev[:255]) If the content is a xml,wml,whtml,... page, this results in exception headers like: Bobo-Exception-Value: <?xml version="1.0"?> <!DOCTYPE ... while most browsers will not barf on this, we encountered numerous problems with wap-gateways refusing to swallow this. Another question is whether it is wise to send things like the file and line numbers where the exception took place to the client. I can understand that it can be useful in debug mode, but I can't see a reason to do this in a production setup. The simplest way of fixing this is to change the code to something like: ev = 'bobo exception' self.setHeader('bobo-exception-value', ev) or to leave out these headers altogether. Romain.