Fix documentation links and improve 404 page

[mdapena]

Initial Checks

• The code compiles successfully without any errors or warnings.
• I have personally tested these changes on my local environment.
• I have ensured that relevant documentation has been added or updated.
• I adhere to the project structure and code standards defined in the documentation.
• My code follows the established coding style guidelines.
• I have added tests for the new code (if applicable).
• All existing tests have passed successfully.

Description

This pull request addresses the broken links in the documentation by setting them to be relative to their current file paths. Additionally, the alignment of the 404 error page has been fixed, and its message has been improved.