You can easily intergrate drupal coding standards, files extention using following file. Netbeans Config.zip
On netbeans,
Goto : Tools->Options
Click on Import, and import two files on this zip archive.

Probleme 1.
If you are activated 'Aggregate CSS files' on admin/config/development/performance, Disable it and refresh the page.
If the page display correctly, Probleme is in CSS Aggregation.

1. Define route in module.routing.yml
Exemple :
module.view.settings:
  path: '/url/to/the/page'
  defaults:
    _controller: '\Drupal\module\Controller\Demo::view'
    _title: ''