Google told us about the causes of sudden drops of a website positions in the SERP (Search Engine Results Page)
John Mueller, specialist of the Google search quality department, said that the sudden change in the SERP site's position is most often associated with updates to the search algorithm, and not with changes made to the site.
Для того, чтобы некоторые изменения вступили в силу, требуется от недели до нескольких месяцев. Обновленный алгоритм начинает работать сразу. Поэтому, если вы внесли в структуру сайта изменения, сайт начнет подниматься или опускаться в выдаче только через некоторое время.
In order for some changes to take effect, it takes from a week to several months. The updated algorithm starts working immediately. Therefore, if you have made changes in the site structure, the site will start to rise or fall in the SERP only after a while
The full answer of the webmaster can be heard in this video (eng):
John Mueller specifies that it is not always a long time for some changes to take effect and not all algorithms start to act quickly. If you, for example, hide your entire site from search, the changes will be visible immediately.
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