HTML - Document flow and rendering order

What it actually means

HTML elements are rendered in the order they appear in the document. This natural flow determines layout before any CSS is applied.

How to use it correctly

Core concepts:

  • Block elements stack vertically

  • Inline elements flow horizontally

  • Source order affects layout, tab order, and screen readers

Example:

<h1>Title</h1>
<p>Description</p>
<button>Submit</button>

This order is respected by:

  • Browsers

  • Keyboard navigation

  • Screen readers

CSS can change appearance, but not logical order.

Why this matters

  • Wrong HTML order breaks accessibility

  • Keyboard users follow DOM order, not visual order

  • Screen readers read top to bottom

  • Many CSS issues are actually HTML structure problems

Reordering with CSS alone creates hidden bugs.

Accessibility impact

  • tab navigation follows document order

  • Screen readers announce content sequentially

  • Visually reordered content confuses users with assistive tech

Practical rule

Always write HTML in the order you want it to be read.
Use CSS only for visual adjustments, not logic.