I wish they went into more detail what exactly changed and why these browsers no longer work, unless it was the PPP protocol they mentioned that is causing the issue.
HTTP 1.1 added the `Host:` header, which let a single IP host many domains, which essentially created the web hosting industry.
You can fix this communication problem with a HTTP 1.1 to 1.0 translating proxy server: http://www.jwz.org/blog/2008/03/happy-run-some-old-web-brows...
1) HTTP 1.0 vs 1.1 and lack of the Host: header, as you've all deduced
2) Additional encoding info tacked on after the Content-type causes parsing issues
3) Many sites now redirect to HTTPS by default. While Netscape 1.0 and Mosaic 1.0 both support HTTPS, it used SSLv1, and well, remember POODLE? :P
Newer versions of these browsers tend to work in native DOSBOX but present problems when running on the web. We're working on it.
Biggest problem right now is that the virtualized dial-up ISP is a bit flaky. For some reason PPP over TCP over Websockets via Trumpet Winsock isn't as rock solid as it should be :P
Bear in mind, though, it will ALWAYS be insecure and it will ALWAYS be more of a "try this out" than popping on your unicycle, starting up your bagpipes and riding down the Information Superhighway permanently.
In order to make these web sites work in the old browsers, it was necessary to
host them specially. In this modern world, a single server will typically host
multiple web sites from a single IP address. This works because modern web
browsers send a "Host" header saying which site they're actually looking
for. Old web browsers didn't do that: if you wanted to host a dozen sites on
a single server, that server had to have a dozen IP addresses, one for each
site. So these sites have dedicated addresses!
The web server also had to be configured to not send a "charset" parameter
on the "Content-Type" header, because the old browsers didn't know what
to make of that.See here for details: http://www.jwz.org/blog/2008/03/happy-run-some-old-web-brows...
HTTP 1.1 (1999, so way postdating Netscape 1.0) has a Host header that's sent with every request, which allows the client to communicate to the server which hostname the client thinks it's talking to. That allows today's world, with multiple hostnames colocated on the same IP, to work properly. But if you leave out the Host header the server doesn't know which of those sites you meant and will do ... something.
For example, this explains the defcon.org failure in their screenshots. In fact, you can try this at home in your favorite command-line:
1) Type
telnet www.defcon.org 80
Trying 162.222.171.206...
Connected to www.defcon.org.
Escape character is '^]'.
GET / HTTP/1.0
3) Repeat, but in step 2 type (or paste, since it closes the connection quickly):
GET / HTTP/1.1
Host: www.defcon.org
Same thing for www.whitehouse.gov (which is in fact a cname for www.whitehouse.gov.edgesuite.net which is a cname for www.eop-edge-lb.akadns.net which is a cname for a1128.dsch.akamai.net which you can bet needs the Host header to know which site you were accessing!).
And same thing for news.ycombinator.com, which is a cname for news.ycombinator.com.cdn.cloudflare.net which then resolves to an IP but doing a reverse DNS lookup on that IP says it's got at least "ns1.cloudflare.com" and "dns.cloudflare.com" as domain names that resolve to it... so it's clearly going to be looking at the Host header to see what you actually think you're talking to. You can even see this if you compare http://news.ycombinator.com.cdn.cloudflare.net/ to https://news.ycombinator.com/ even though one is a cname for the other.