trying to link two or more pages in html but error loading page

I'm building my blog, I have done everything perfectly, but when it came to linking two pages, it gave me this error

error loading page

however, I have made sure that all my files are in the same directory!

<ul class="flex-lg flex-lg-row justify-content-lg-center align-content-lg-center">
    <li class="current-menu-item"><a href="index.html">Home</a></li>
    <li><a href="travelling.html">Travelling</a></li>
    <li><a href="health.html">Health</a></li>
    <li><a href="#">Photos and videos</a></li>
    <li><a href="#">about me</a></li>
    <li><a href="contact.html">Contact</a></li>
</ul>

here is my code

what is the problem?