There’s an invalid URL in page Creating your Own Puzzle.
Its text is In/Out Puzzles in the Types of Contributions section.
I think it should take me to this page: https://www.codingame.com/playgrounds/40701/help-center/inout-puzzles
You may have slightly more luck to have the issue fixed if you report it in Discord’s bug report channel, as it seems that the current CG team seldom reads the forum.