Passage: The purpose of HTML markup is to describe a document's structure, not its programmatic behavior. Combining the two can negatively impact a site's maintainability, like combining content and presentation. JavaScript behavior created and referenced in the HTML can be harder to use and maintain, for example when setting handlers for several events on a single element, when setting the same event handler on several elements, or when using event delegation.

Question: HTML markup describes what aspect of a document?
document's structure