On the website you are given "ссылочная масса" is defined as "the total number of links to the particular website from all external resources" (совокупность ссылок со сторонних ресурсов). However, out of context this expression can also mean "link weight" (вес/значимость ссылки) as Alena has mentioned above. I would translate "применение стратегий управления ссылочной массой" as "using strategies to manage the amount of links from external resources".

I suppose "ссылочная масса" is the same as "Link Equity" or "Link Weight". Link Equity: Link equity, also known as link weight, link value or link juice, is the amount of value a link passes through when linking out to another web page. Google has deemed that every link holds different value based on the authority of the website linking out. An incoming link from a highly authoritative website would hold more link equity compared to a website with minimal credibility and authority online. (from here http://www.bigvisionseo.com.au/seo-glossary ) Alexandra, is that what you wanted to find out? I hope I understood your question correctly.