Original HTTP (now called 0.9) did not have headers in the request. HTTP 1.0 added headers, including the "Content-Type" header (reused from the MIME e-mail st

Original HTTP (now called 0.9) did not have headers in the request. HTTP 1.0 added headers, including the "Content-Type" header (reused from the MIME e-mail standard), specifying the type of the data being transferred. Before that, all data was indeed implied to be HTML and nothing else.