A standard semantic layout follows a predictable hierarchy. The <header> identifies the top of the page, usually containing your branding and navigation. The <main> tag is the singular heart of your document, containing the core content unique to that page. You should never have more than one <main> tag per page. The <footer> anchors the bottom, housing copyright, secondary links, and contact information. This logical structure empowers browsers and assistive tech to instantaneously 'map' your page.

Understanding the difference between <section> and <article> is a core architectural skill. Use a <section> to group related thematic content together—like a 'Features' section or a 'Contact' block. Use an <article> for content that is entirely self-contained and could theoretically be syndicated independently (such as a blog post, news story, or product review). If the block can exist on its own without losing meaning, it fundamentally belongs in an <article> tag.

The <aside> tag is leveraged for content that is 'tangentially' related to the primary narrative. Think of sidebar ads, author biographies, or supplementary links. It injects vital context without polluting the core reading flow within the <main> area. Screen readers isolate the <aside>, allowing users to intelligently skip it. Similarly, the <nav> element designates a block strictly for major navigational links. It acts as an unmistakable landmark for assistive tech to locate the site's primary menus.