A "404 page" is the error message that users see when they try to view a page that doesn't exist on your site. This can happen if they follow an outdated link, or type in a web URL incorrectly.
This one, from Finalsite.com, lets users know that they've made a mistake with the address and invites them to click back to our home page. This simple, clean approach to 404 pages is common, although some websites put a little more creativity into theirs.
If you want to create a custom 404 page that's more engaging, you can do that easily. You may want to have a 404 page that utilizes your site's style for a more integrated experience. Another option is to automatically redirect users to the site directory, which is handy for site users who may be having trouble locating a specific site page.
To set a 404 page for your school, first click on the Domain Settings.
Click on the Action Menu on the blue bar in Composer that's at the top of the list of site page, then select "Settings."
On the Domain Settings window, select the "Landing Pages" tab.
Find the "404 Page" entry, and click "Choose Page."
A new menu will appear; you can create a custom 404 page and choose it, or select any other page on your site to be the 404 page. Whenever a visitor attempts to access a site page that does not exist, they will be redirected to the page you select here.