I will be grateful for the help. I am watching lecture7. I have saved hello.html, and started the apache50, did all steps described in the lecture; but when I tried to access either https://ide50-myname.cs50.io/ or https://ide50-myname.cs50.io/hello.html from another browser, the Chrome, it demanded my login details for cs50.io. I understand that it's fine, because my files are stored there, but I didn't understand how can hello.html be accessed from the web, if it is saved on my server and only a person with my login details can enter it. Thank you!
If your workspace is public, it is accessible to anyone on the web without your login details. You can see the setting in CS50IDE -> Go To Your Dashboard.
I reserve the right to change/delete my answer if you discover that your workspace is public. Further, by no means am I suggesting that your workspace should be public. I believe it should be private.