The first (and easiest) way that a user can be blocked by a website is to simply block the user name and password from being accepted. This only works if you have to sign into some kind of account
How to fix a website with blocked mixed content - Web If your website delivers HTTPS pages, all active mixed content delivered via HTTP on this pages will be blocked by default. Consequently, your website may appear broken to users (if iframes or plugins don't load, etc.). Passive mixed content is displayed by default, but users can set a preference to block this type of content, as well. How to Block Websites on Computer Windows 10? Sep 02, 2017
You can block messages from specific email addresses or domains from reaching your inbox. When you add an email address or domain to your blocked senders list, Outlook on the webautomatically moves messages from that sender to the Junk Email folder. Note: You can have up to 1,024 addresses or domains in the blocked senders and safe senders lists.
Is your website blocked?
How to Block Websites on Mac with Screen Time
How to Block Any Website On Your Computer, Phone, or Sep 09, 2017 Block Websites on Microsoft Edge in Windows 10 (Host's Sep 19, 2019 How To Block Websites in Chrome [July 2020] Jul 05, 2020