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.
If you can rely on the name of the protocol as an accurate description, then LDAP would actually be "lightweight", UDP packets would be assembled by users, and SSL would be secure.
If HTTP represents documents as text, then the "hypertext" part of the name becomes misleading, because you can't put hyperlinks in plain text. That is: the protocol is misnamed, because the leading "HT" stands for "Hypertext", not "Hyper Text". It's designed to transfer HTML.
> If you can rely on the name of the protocol as an accurate description, then LDAP would actually be "lightweight", UDP packets would be assembled by users, and SSL would be secure.