<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>{{ page.title }}</title>
    <link href="../css/mminail.css" rel="stylesheet">
</head>

<body>

<header class="masthead">
	<aside id="navigator">{% include nav.htm %}</aside>
	<h1>MMINAIL.GitHub.io Directory</h1>
</header>

<h2>{{ page.title }}</h2>
	<hr />

<div id="container">

	<article id="main-article">
		{{content}}
	</article>

</div>

<footer>
	{% include footer.htm %}
</footer>

</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>{{ page.title }}</title>
    <link href="{{site.baseurl}}/css/mminail.css" rel="stylesheet">
</head>

<body>

<header class="masthead">
	<aside id="navigator">{% include nav.htm %}</aside>
	<h1>MMINAIL.GitHub.io Directory</h1>
</header>

<h2>{{ page.title }}</h2>
	<hr />

<div id="container">

	<article id="main-article">
		{{content}}
	</article>

</div>

<footer>
	{% include footer.htm %}
</footer>

</body>
</html>
Add site baseurl to css link in head tag
Add site baseurl to css link in head tag

To create a relative link in Jekyll, pre-pend the hyperlink with ...
\{{site.baseurl}}/
