HTML5 best practices
1. Declare the correct DOCTYPE.
2. Use lowercase element names.
3. Close your paired tags.
4. Put attribute values in "quotation marks".
5. Use indents and extra lines for readability.
6. Use comments for documentation.
7. Check spelling.
8. Do not use the html font element and avoid inline styles.
9. Validate.
10. Save and preview in a browser often.