This panel displays HTTP Request and Response Headers for each element shown in the Transaction Performance Details view. As you select each page element in the Transaction Performance Details view, the Request and Response headers associated with the element are displayed.
HTTP Headers are only shown after the currently open script has been played during the current session.
The Selected Measurement Object HTTP Headers view displays all the details available for both request and response headers.
Documentation for HTTP headers can be found at http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html