If you are disavowing links on a URL level it is important to have an understanding of iframes and how they work.

An inline iframe is used to embed another document within the current HTML document.

The page www.domain.com/tesimonials.html could contain an iframe which embeds the HTML document www.domain.com/entires.html.

An inexperienced link analyst may find a link on www.domain.com/tesimonials.html that they wish to remove. Ergo, this URL is then disavowed by the link analyst.

The page www.domain.com/entires.html though may also contain links to the domain that are not wanted. Often the raw URLs of embeded iframes are not disavowed.

To be completely sure that Google understands what links need to be no longer taken into account we would recommend disavowing the embed URL as well as the page that embeds this URL.

Guestbook links are an example of link types that often make use of iframes.