First of all, what you're posting is not HTML. It's php. Different animal entirely.

Secondly, you're apparently editing the files in the classic folders instead of creating your own custom template. If you continue to do that, all your changes will be lost with the next upgrade/update because the contents of the classic folders will overwritten unless you are willing to spend a few hours comparing files.

HEADING_TITLE is defined in a lot of places. Check includes/languages/english/index.php (if you're using the override/template system correctly, it'll be includes/languages/english/YOUR_TEMPLATE/index.php) at around lines 51 and 55.

Check the same file for TEXT_GREETING_GUEST around lines 13 and 15.