Misago/misago/emberapp/app/templates/error-404.hbs

<div class="error-page error-404">
  <div class="container">
    <div class="error">

      <div class="error-icon">
        <span class="fa fa-compass"></span>
      </div>

      <div class="error-message">
        <p class="lead">{{gettext "Requested page could not be found."}}</p>
        <p>{{gettext "The link you clicked was incorrect or the page has been moved or deleted."}}</p>
      </div>

    </div>
  </div>
</div>