Service Manager Self-Service Portal Stylesheets not interpreted

When I recently installed Service Manager 2016 Technical Preview 5, I also installed the new out of the box Self-Service portal. However after installation finished successfully, I experienced an odd behavior: The portal did no show up in it’s usual design.

As you can see below, the CSS stylesheets were transferred with the wrong MIME type text/plain which caused the portal to be unusable for users.

Luckily the error pretty much tells you everything you need to know to resolve the issue :-)

In IIS, the Static Content feature is responsible for serving the static contents of a website like images, scripts , style sheets, etc. The portal installer unfortunately does not seem to check whether the IIS HTTP Feature Static Content is installed or not. Of course it was not…

Installing the feature _Web Server (IIS) - Web Server - Common HTTP Features - Static Content _did the trick and the portal turned on the full power of its personality :-)