Pragma is a string property that contains HTTP server directives, and represent optional behavior for the HTTP protocol. Pragma normally contains the value "no-cache" and indicates that the HTTP request should be forwarded to the server even when the request can be satisfied from the server cache. 

Pragma is used in an HTTP client request, and has the same meaning as the CacheControl property used in HTTP/1.1. Pragma is defined to provide backward compatibility with HTTP/1.0. 

Pragma may also contain implementation-specific extension values which are defined in the HTTP protocol. Pragma directives must be passed by a proxy or gateway application, regardless of their significance to that application, since the directives might be applicable to all recipients along the request/response chain. It is not possible to specify Pragma for a specific client. Any Pragma directive not relevant to the client should be ignored. 

Use of Pragma in a HTTP response is not defined by the HTTP protocol, and does not provide a reliable replacement for CacheControl in the response.

TIdEntityHeaderInfo.CacheControl