Removing the grey line of the lateral sidebar ?

Hi,

On the general options, i didn’t found a way to work only on a plain page.
I can put the sidebar to 0% and the content to 100%, and choose the “full page” option below, I see a grey line on the right of the page, as a frontier beetween content and virtual widget sidebar.
Any idea to remove this grey line ?

Thanks !

The page I need help with: [log in to see the link]