Our sites are served through two main locations:
- the actual websites at (e.g.) stackoverflow.com which contain only the text of the pages
- a static resource website at http://cdn.sstatic.net/ which contains images, style, and other resources.
This is an optimization due to the way browsers work.
Apparently you are behind a misconfigured firewall which is letting through the first website but blocking the second website.
You can see that this is the case in this error you reported:
Error Code: 502 Proxy Error. Forefront TMG denied the specified Uniform Resource Locator (URL). (12202). IP Address: 172.17.94.40 Date: 2016/01/21 11:26:32 AM [GMT] Server: MWPTMG01.elec.eskom.co.za Source: proxy
You need to ask your internal support to allow connections to
*.sstatic.net on HTTP and HTTPS ports in the "Forefront TMG" instance running on