In google webmaster at fetch as google i have this....

HTTP/1.1 200 OK
Date: Tue, 19 Mar 2013 09:58:19 GMT
Server: Apache
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
X-Mobilized-By: WordPress Mobile Pack 1.2.5
Set-Cookie: PHPSESSID=67091e412b69efc8b799eadd4191cde6; path=/
Set-Cookie: wpmp_switcher=desktop; expires=Wed, 19-Mar-2014 09:58:19 GMT; path=/
Keep-Alive: timeout=5, max=75
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8

.....html code ...

Why is that
Expires: Thu, 19 Nov 1981 08:52:00 GMT ???