I sniffed an
Follow TCP stream
Follow HTTP stream
There are several possibilities. One of the primary is that you are looking at gzipped content, which is very typical from web servers these day, allowing them to send the page back in a compressed state. If this is the case, look for the
Content-Encoding: header and examine its value.
The other possibility is that the application is streaming binary data through the HTTP connection, even though the application is setting
text/html. There's nothing that makes this illegal, though it is a bad practice since this header acts as a hint for the browser to determine how to handle the data.