themes-wordpress/block-canvas/templates/404.html

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<main class="wp-block-group" style="margin-top:var(--wp--preset--spacing--80);margin-bottom:var(--wp--preset--spacing--60)"><!-- wp:heading {"textAlign":"center","level":1,"fontSize":"x-large","anchor":"oops-that-page-can-t-be-found"} -->
<h1 class="wp-block-heading has-text-align-center has-x-large-font-size" id="oops-that-page-can-t-be-found">Oops! That page can’t be found.</h1>
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<p>It looks like nothing was found at this location. Maybe try a search?</p>
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<!-- wp:search {"label":""} /--></main>
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<!-- wp:template-part {"slug":"footer","tagName":"footer"} /-->