The Content-Type entity-header field indicates the media type (or MIME type) of the entity-body sent to the recipient or, in the case of the HEAD method, the media type that would have been sent had the request been a GET.
Content-Type = "Content-Type" ":" media-type
An example of the field for HTML documents is:
Content-Type: text/html; charset=ISO-8859-4
For a PNG file, it would be: