What are the factors that affect the value of external links?

The factors that can affect the value of external links are listed below:

The link’s location on the page in relation to other links (is there a lot of other links around it? Is it contained within body content with no other links?).

The trustworthiness of the source domain name (based on the iterative calculation of the link distance to the trusted seed website, that is, TrustRank).

The amount of PageRank that a link transfers (i.e. the transferable PageRank that a page has divided by the number of links on the page).

The overall authority and importance of the source domain name (based on iterative calculation of the entire site's links).

The link location is within the main content of the page (not side navigation, footer, etc.)

The topic relevance of the linking source page to the target page.

Link text uses keywords (matches the search terms).

The quality of other outbound external links on the page.