How to fix landmark complementary is top level on BigCommerce

Steps for BigCommerce

1. In your BigCommerce admin, go to Storefront → Themes → click 'Advanced' → Edit Theme Files (Stencil CLI recommended for safety).
2. Locate the Handlebars template where the sidebar renders — commonly `templates/components/common/sidebar.html` or inside a page template like `templates/pages/product.html` or `templates/pages/category.html`.
3. Find the `<aside>` block. If it is nested inside `{{{region name="main"}}}` or a `<main>` element, cut it out and paste it as a sibling of the `<main>` block in the same parent template.
4. Ensure the parent wrapper `<div>` contains `<main>` and `<aside>` as siblings, then apply a two-column CSS layout (Flexbox/Grid) in `assets/scss/` to restore the visual appearance.
5. Add `aria-label="Sidebar"` or a descriptive label to the `<aside>` tag.
6. Bundle and upload the theme, preview on a staging URL, and validate with the axe browser extension.

What is landmark complementary is top level?

Landmarks are special HTML "signposts" that screen readers use to let users jump directly to major sections of a page — the header, main content, navigation, footer, and sidebars. The "complementary" landmark (created by an `<aside>` tag or `role="complementary"`) is meant to mark supporting content that stands on its own alongside the main content, like a sidebar, related-links panel, or promotional widget. The WCAG rule "landmark-complementary-is-top-level" fires when that `<aside>` is placed inside another landmark (for example, inside a `<main>`, `<header>`, or `<section>` with a role), rather than sitting directly inside the `<body>` at the top level of the page.

Screen reader users — including customers with visual impairments — rely on landmark navigation to quickly skip around a page without listening to everything. When a complementary landmark is buried inside another landmark, screen readers either misreport its purpose or completely hide it from the landmark list, making it impossible for these users to find your sidebar content (promotions, related products, trust badges, support widgets) efficiently. This is a WCAG 2.1 Success Criterion 1.3.6 (Identify Purpose) and best-practice landmark structure issue, and repeated accessibility failures create legal exposure under laws like the ADA (US), EAA (EU), and AODA (Canada). Fixing it improves the experience for the roughly 7 million screen reader users in the US alone, reduces legal risk, and signals to Google that your page is well-structured.

See the complete Landmark complementary is top level guide for every platform and the full background.