An advertisement appeared on my site, although I did not order it, and did not insert it into the co

http://jnbc.rf.gd

When you open the site, a page appears that I wrote (as it should), but then either a banner or a full-screen advertisement appears, but I did not add it

For me your website works fine without any ads whatsoever:

Maybe you have a proxy configured and enabled on your computer that adds ads on any HTTP website you visit; you might consider removing that proxy configuration or adding HTTPS to your website if you don’t want that ad to pop up on your side.

Then another question is how to go from http://jnbc.rf.gd to https://jnbc.rf.gd? How to migrate it?

It’s easy! Just follow this article as it is a step-by-step tutorial, with also a video attached even if old:

It also includes other guides you can also find on the documentation, such as this:

and this:

which are also helpful.