CSS Pocket Reference, 3rd Edition

Replaced Elements

In contrast, replaced elements are those whose content is replaced by something not directly represented by document content. The most familiar XHTML example is the img element, which is replaced by an image file external to the document itself. In fact, img itself has no actual content, as we can see by considering a simple example:

<img src="howdy.gif" alt="Hi" />

There is no content contained in the element—only an element name and attributes. Only by replacing the element’s lack of content with content found through other means (in this case, loading an external image specified by the src attribute) can the element have any presentation at all. Another example is the input element, which may be replaced with a radio button, checkbox, or text input box, depending on its type. Replaced elements also generate boxes in their display.