iFrame Sandbox Permissions Tutorial (edit)
https://benohead.com/ (HTML+CSS+JavaScript)
https://www.geeksforgeeks.org/ (HTML+CSS+JavaScript)
https://looker.com/blog/iframe-sandbox-tutorial
https://github.com/JimRottinger/sandbox_sandbox
Cookie
https://stackoverflow.com/questions/3342140/cross-domain-cookies
How to detect ... using JavaScript ?
https://www.geeksforgeeks.org/detect-the-operating-system-of-user-using-javascript/
https://www.geeksforgeeks.org/how-to-detect-html-5-is-supported-or-not-in-the-browser/
https://www.geeksforgeeks.org/how-to-detect-the-users-device-using-jquery/
CSS
https://www.geeksforgeeks.org/jquery-get-and-set-css-classes/
C#
JavaScript
https://www.geeksforgeeks.org/javascript-tutorial/
https://www.geeksforgeeks.org/javascript-string-slice/
https://www.geeksforgeeks.org/how-to-refresh-a-page-using-jquery/
How to ... using CSS
https://www.geeksforgeeks.org/how-to-give-a-div-tag-100-height-of-the-browser-window-using-css/
https://www.geeksforgeeks.org/javascript-detecting-a-mobile-browser/
https://www.geeksforgeeks.org/difference-between-cache-and-cookies/
https://www.geeksforgeeks.org/javascript-interview-questions-and-answers/
https://www.geeksforgeeks.org/javascript-interview-questions-and-answers-set-2/
https://www.geeksforgeeks.org/javascript-interview-questions-and-answers-set-3/