Microsoft products do not support comments within footers, footnotes or headers. WordPad does not support some RTF features, such as headers and footers. OS commands; XML parsers, SMTP headers, program arguments, etc. The filesizes indicated below include the internal JPEG information headers and some metadata. HTTPS encrypts all message contents, including the HTTP headers and the request/response data. The POSIX standard added several nonstandard C headers for Unix-specific functionality. The engine was also fitted with stainless steel "shorty" headers. The transmission overhead consists of preamble sequences, frame headers and acknowledge packets. Any bytes after the headers in the packet are considered the message body. These vary in whether they affect HTTP headers or HTML content. The diff format allows for irrelevant "headers", such as mbox data, to be added. Racing style tubular headers replaced the standard cast iron headers. Many spam-filtering techniques work by searching for patterns in the headers or bodies of messages. Engine performance increase comes largely from the long tube headers and a revised ECU. Browsers identify themselves by "User-Agent" HTTP headers.