naringsliv It relates to both article layout and the template that you're using together.
For example, the above article page: /butikk-handel/lett-a-velge-kassaleverandor is using layout which includes the sidebar in the right.
However, the menu item of this page is a special menu item type of Magazine layout
which also offers option to set layout for the article detail page:
The current layout also displays sidebar so you see both of them.
So you can either change the layout as I suggested above or switch to other layout for article detail page.
Regards