Final answer:
When the primary HTML5 assets get delayed, a polite load image is displayed in the user's browser as it is loading. If a polite load image is not available, a default ad may be shown.
Step-by-step explanation:
When the primary HTML5 assets get delayed, a polite load image will usually be displayed in the user's browser as it is loading. This is a small, low-resolution image that is designed to load quickly and provide a visual indication that the content is still loading. Once the primary assets are loaded, they will replace the polite load image.
In some cases, if a polite load image is not available or cannot be displayed, a default ad may be shown instead. This is typically an advertisement that is configured to be displayed when content is not yet available.
If neither a polite load image nor a default ad is available or can be displayed, a backup image may be shown. This is an image that is intended to be a placeholder and provide a visual representation of the content until it is fully loaded.