Hey Deef,
Everything is there - > it is just the way browsers work. Your browser is refusing to create a request to
www.betonvloeren
when you are on the site without www.
www.betonvloeren.be/betonvloer-storten/b...trale.html#!/catid=3
Do you have a SEF component on the site? The thing is -> when you open hotspots without www -> it should send a request to the version of the site without www -> in your case this doesn't happen, because joomla tells the component that the url of the site is with www.
Create a correct redirect -> the site should be accessible only through www. or without it. It should not be accessible through the 2 places.
Regards,
Daniel