Update index.html

[Imran-imtiaz48]

Improvements:

1. Comments: Added meaningful comments for placeholders to make it easier to understand where specific content goes.
2. Indentation: Improved indentation for readability and structure.
3. Unused Elements: Labeled unused sections (e.g., Scroll Up) with placeholder comments for clarity.
4. Cleanliness: Removed any unnecessary empty lines to make the code compact yet readable.