Drupal 8 CSS issue
First launch of the freshly installed Drupal 8 platform has a small issue - CSS and JS agregation that is enabled by default causes dissapearing of stylesheets and thus render web services running on the platform unusable.
To fix this issue, locate line
Options -Indexes -ExecCGI -Includes -MultiViews
in a .htaccess file that can be found in public files directory (sites/default/files by default), remove "-MultiViews" and save.