According to the HTTP/1.1 spec the order of header fields with different names is insignificant, but as usual, Microsoft has outdone themselves. I am streaming a PDF directly to the web server and IE version 5.01 sp1 and above will accept the following header in this order only: Accept-ranges: bytes Content-Length: 3612 Content-type: application/pdf Unfortunately this is not the order send_http_header sends the fields, so I am left scratching my head. Is there a way to force header field ordering short of printing it manually? thanks, Kiriakos