Your comments

The web server is IIS 8.5 running on Windows server 2012 R2.
It is being NATed by a pfSense based firewall. Port 80 is forwarded to IIS which in turn uses the HOST http header to route to the correct web site.

It's available via both IPv4 and IPv6
ICMP is not blocked. Also according to this MTU test page (http://www.letmecheck.it/mtu-test.php). According to that test 1500 is the max size I can have and still not fragment the packages.

Open the page and enter paks.no as target and test yourself.
Mats: Can you ask the techs what MTU I should use? I'm running pfSense as a firewall with the default WAN MTU settings (1500 bytes). Must confess that this is a bit above my networking understanding.
Yes. Since both ping and traceroute works the only thing I can figure is that your company has a proxy or antivirus that stops the web traffic. Usually those are used to stop employees accessing gambling, porn or similar sites. And most often you are told that site so and so was blocked because it is against company policies.
Nope. Nothing for 192.36.162.* either.

There is nothing on Tellmon that should cause it to be blocked. I'm not doing anything fancy, not should the address be blocked by any filters. Could you have a colleague try from another computer on the work network? Good to know if it's an issue with your computer or the whole network.
Very strange. No mention of 158.39.96.* in any of the IIS log files, so you are simply not reaching the server.
I've turned on default binding, can you see if you can reach anything now?
The headers seems fine. Checked the firewall logs and no mention that anything from 158.39.96.* has been blocked either.
Can you check if you can reach http://paks.no or http://crashtest.ninja as well? These are two other web sites running on the same server.

According to https://www.site24x7.com/public/t/results-1431343994872.html the web site is available from all locations (except one, but a retest showed that working as well).

I suspect you are running some software on your computer what prevents you from accessing the site.
I can't find any errors in the log, but I can delete your account manually. Is csom@molltorp.nu your username?