hugo-theme-introduction/layouts/404.html

 {{ partial "header.html" . }}

<div class="container-fluid">
    <div class="main">
        <div class="page-head-box fade-in one">
        <h1 class="list-title">404</h1>
        
            <div class="blognav">
            <hr>
            <a href="/">Main</a> | 
            <a href="/#about">About</a> | 
            {{ if .Site.Params.showprojects }}
            <a href="/#projects">Projects</a> | 
            {{ end }}
            {{ if .Site.Params.showallposts }}
            <a href="/#blog">Back to blog</a> |
            {{ else }}
            <a href="/blog">Back to blog</a> |
            {{ end }}
            <a href="/#contact">Contact</a> 
            <hr>
            </div>
        </div>

    <div class="content fade-in two">

    <div class="container markdown">
        Oops! Either you've found a bug (in which case, <a href="{{ .Site.Params.email }}">please tell me</a>) or you're just making things up. This page doesn't exist!
    </div>
            
            <div class="blognav">
            <hr>
            </div>
{{ partial "footer.html" . }}
</div>
</div>
</div>