There's no form here, so we should be using formBox. Instead, use the same template structure as the Activation failed template (with the alternate links column.

Use the following content:
*header*
{code}
<h1>Error 404 <small>Page not found</small></h1>
{code}

*content*
"The page you have been requested could not be found or has been removed. You can either return to the \[link:home page] or use the links to the right."

*quick links*
- Profile
- Saved Search
- Home