Where can I read about the link shorthand (without http:)?

Question

HTML

Here are some examples to make it clear what I'm talking about:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script src="//api-maps.yandex.ru/2.1/?lang=ru_RU" type="text/javascript"></script>

In these examples, the protocol (http or https) is not indicated in the url, but instead it is //
Why do they do this?

Answer 1

This is done in order to ensure that the remote resource is requested using the same protocol that is present on your site. So that there is no situation when everything is https, but a remote resource is requested via http, which, as it were, contradicts. Just a generic solution.