Does it pop up for any 404 error? If so it might be some script or font or whatever resource the site itself is using that would otherwise fail silently. If not

Does it pop up for any 404 error? If so it might be some script or font or whatever resource the site itself is using that would otherwise fail silently. If not... then there has to be some other bug/issue because i get it for many different sites that shouldn't have it.