By default, Uscreen provides a generic 404 page for all sites - no further action is needed if you're content with the Uscreen default 404 page.
To brand your 404 page, you can add the following code with your personal modifications to the Head Code section of the Code Snippets. This 404 page will display your site's logo by default and will be presented for any 404 page on your site. If you wish to further customize this and aren't familiar with basic HTML/CSS, you'll need to hire a developer.
<script> let detect404Page = () => { let notFoundContainer = document.querySelector('.not-found') if (notFoundContainer) { if (!notFoundContainer.classList.value.includes('touched')) { let markup = 'ADD YOUR OWN TEXT' let description = document.querySelector('.not-found .description') description.innerText = '' description.insertAdjacentHTML('afterbegin', markup) notFoundContainer.classList.add('touched') } } setTimeout(() => detect404Page(), 500) } detect404Page()</script><style> .not-found { margin-top: 13vw !important; } .not-found .brand-logo { max-height: 150px; } .not-found .error-image { display: none; } .not-found .title-area, .not-found .description { font-size: 0; } .not-found.touched .description { font-size: 20px; text-align: center; max-width: 800px; } .not-found .description { margin-top: 10px; } .not-found .title-area:before { content: 'ADD YOUR OWN TEXT HERE'; font-size: 35px; }</style>