The default presentation of details elements is fine for dialog boxes and other cases where the content wants to emulate the platform or browser. However, authors of other content will want to customize its presentation; for example, one may want to replace the browser's widget (usually a triangle) with an icon that is more suggestive of its function (such as a question mark in a circle for displaying a definition). If HTML5 does not permit this, authors will use custom scripting rather than standard controls, which can render them incompatible with assistive technology and reduce the ability of users to customize them using browser settings, browser add-ins, or user style sheets.

Similarly, ideally an author-provided or user-provided style sheet would be able to adjust certain aspects of the detail element's presentation, such as the height of the control widget and perhaps overriding the open attribute.