A page can embed another website in a frame. Many sites don’t allow this, to protect you from tricks such as invisible buttons layered over their page, so Hominis shows a message where the embedded site would be: it will not display the page if another site has embedded it.
It only affects the embedded part. To see the site, open its address directly: right-click the link and choose Open link in new tile, or type the address in the command bar.