When your company's boards or certain board items are set to be Offline, their links will lead to 404 pages- "Page Not Found".
To customize your company's 404 page:
1. Navigate to your company's admin page
2. In the settings tab switch the toggle to enable company's 404 page.
3. Upload the company's logo and choose a default URL that you would want to direct your customers to.
Note: use the test link on the bottom to test your customized 404 page.