If I take a remote resource (.js, .css, .jpg...) via https, and the site with the resource is available via http. Or vice versa. Is it always possible to take?

Question

css

I want to use protocol-relative links everywhere on my site:

<script src="//example.com/script.js" type="text/javascript"></script>

Since there is ssl on the prod, but it is not on the local server.
I have a question. If I take js, css, jpg... and other files from other sites in this way. Will this always work?
The protocol-relative link substitutes the protocol that is currently used on my site. For example, if I have http on my site, then http will be substituted.
And if I want to get a resource from another site. And the other site works on https. Will I succeed?
And vice versa - if my site is on https and the other is on http.
Will it always work or does it depend on the developer of the other site - did he redirect to .htaccess or not? Or from something else?
I can test it myself, but I don't know all the settings of different servers (apache, nginx...). Maybe it will work for me. But then somewhere - no. Because of what there will be a bug that I or another developer will look for a long time.

Answer 1

Normal div slider, arrows - switches, day - slide.

Answer 2

depends on how the remote site handles requests.

Answer 3

The browser will swear (in the address bar it will show redness, saying that there is no trust in the site), but it will do so.