Interesting Headers

The response headers returns with Google’s logo looks like this:

Content-Type: image/gif
Last-Modified: Mon, 25 Apr 2005 21:06:18 GMT
Expires: Sun, 17 Jan 2038 19:14:07 GMT
Server: GWS/2.1
Content-Length: 8558
Date: Sat, 16 Jul 2005 01:52:05 GMT

And for some gif served by IIS on Win 2003 Server looks like this:

Server: Microsoft-IIS/5.0
X-Powered-By: ASP.NET
Date: Sat, 16 Jul 2005 02:08:59 GMT
Content-Type: image/gif
Accept-Ranges: bytes
Last-Modified: Fri, 04 Mar 2005 09:12:29 GMT
Etag: "20bb944a9a20c51:acc"
Content-Length: 3779

You can get this by using Web Developer Toolbar’s Information > Reponse Header button in Firefox.

Interesting things are:

1. Google is not using Cache-Control: max-age=xxxx header which tells browser to cach the image for a while and not re-request from the server again. This is surprising because you would think Google would use every possible way out there to reduce the load on their server.
2. Google has named their custom web server as Google Web Server, not surprisingly.