character encoding

I insert the following META element into most of my pages:

<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">

When validating, I get the following message:
--
Character encoding: iso-8859-1 The character encoding specified in the
HTTP header ("") is different from the one specified in the META element
("iso-8859-1"). I will use "iso-8859-1" for this validation.
--

What is "HTTP header ("")? Have I incorrectly marked up this particular
META tag?

Thanks,
Cindy K. Stanley
Stanley Support Service

HTML: hwg-basics mailing list archives, maintained by Webmasters @ IWA