If the sidebar contains a sidebar menu, it should come before the main content so the menu can appear collapsed at the top of the page in small viewports.
<div class="mzp-l-content mzp-has-sidebar mzp-l-sidebar-left">
<aside class="mzp-l-sidebar">
<nav class="mzp-c-sidemenu">
<section class="mzp-c-sidemenu-summary mzp-js-toggle" aria-controls="sidebar-menu">
<h3 class="mzp-c-sidemenu-label">Menu label</h3>
<ul>
<li>Menu title</li>
<li class="mzp-is-current">Menu item one</li>
</ul>
</section>
<section class="mzp-c-sidemenu-main" id="sidebar-menu">
<h4 class="mzp-c-sidemenu-title"><a href="#">Menu title</a></h4>
<ul>
<li class="mzp-is-current">
<a href="#">Menu item one</a>
</li>
<li><a href="#">Menu item two</a></li>
<li><a href="#">Menu item three</a></li>
</ul>
<h4 class="mzp-c-sidemenu-title"><a href="#">Second menu title</a></h4>
<ul>
<li>
<a href="#">This menu item has a longer label that will wrap to a few lines, please don’t do this</a>
</li>
<li><a href="#">And one more menu item</a></li>
</ul>
</section>
</nav>
<script src="../../protocol/js/sidemenu.js"></script>
<script>
window.MzpSideMenu.init();
</script>
</aside>
<main class="mzp-l-main">
<h1>Welcome to the main content</h1>
<p>The sidebar comes <strong>before</strong> the main section in the source order.</p>
<h2>Heading Level 2</h2>
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<h3>Heading Level 3</h3>
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</main>
</div>