First can you check that when you saved the changes to index.html the file did not get renamed as index.html.txt
Make sure you have the you have UNCHECKED the this option "Hide extensions of known file types" in Explorer's Folder Options.
If this is the error then you really need to get a semi decent editor and stop using notepad. Try downloading Notepad++, it good and free.
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(Windows 10 Pro 64bit) (Wampserver 3.3.4 64bit) Aestan Tray Menu 3.2.5.4
<Apache versions MULTIPE> <PHP versions MULTIPLE> <MySQL Versions MULTIPLE>
<MariaDB versions MULTIPLE> <phpMyAdmin versions MULTIPLE> <MySQL Workbench 8.0.23>Read The Manuals Apache --
MySQL --
PHP --
phpMyAdminGet your Apache/MySQL/mariaDB/PHP ADDONs here from the
WAMPServer alternate Repo-X-X-X-
Backup your databases regularly Here is How dont regret it later! Yes even when developing -X-X-X-