Archived posting to the Leica Users Group, 1998/12/15
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It is technologically possible to configure a WWW server so that it
behaves differently depending on how you arrived at a page.
When a web server is asked to provide a page, it is given the following
information:
* IP address of the computer making the request. Usually this is your PC
or Mac or whatever.
* The name of the page being fetched.
* The name that the requestor thinks the computer has. (This trick allows
one computer to pretend to be many different computers).
* The protocol level (e.g. HTTP/1.1, or whatever)
* The URL that the requestor was looking at when the page was requested.
If you are looking at the web page for St. Paul's Cathedral and then
suddenly decide that you want to look at the Leica page, and you type
the address of the Leica page by hand into your browser, the result (as
seen by the Leica page's web server) is the same as if there had been a
link to that page on the St. Paul's Cathedral page and you clicked on
it.
* The name and version number of the browser being used.
Normally this information is just written to a log file that is looked
at later, but it is possible to program the web server to give
different responses depending on the value of any of those fields. The
most common use of this capability is to make a web site that reacts
differently to Netscape and Internet Explorer, but one can just as
easily program it to react differently if you got there from Boy Links
or from St Paul's Cathedral.
Saying that it is possible is not the same as saying it is easy. This
kind of programming is, while not conceptually difficult, quite tedious
and requires a high level of skill and precision in arcane scripting
languages. It would surprise me if a hosting site like Tripod were
willing to provide such a service.
By the way, I run (on the computer right here at my knees) the
web site for St. Paul's Cathedral London ( see
http://stpauls.london.anglican.org ). Who would ever know that
the web site for St Paul's, London, is at some guy's house in
Palo Alto, California? Ah, the wonders of the Internet. If any
of you Leica folks are of the Anglican/Episcopal persuasion, you
might want to take a look at my WWW magnum opus,
http://anglican.org/
Brian Reid