The HTML <small> element makes the text font size one size smaller (for example, from large to medium, or from small to x-small) down to the browser's minimum font size. In HTML5, this element is repurposed to represent side-comments and small print, including copyright and legal text, independent of its styled presentation.
Consider:
<img src="image.jpg" alt="London by night">
<small>The copyright of this image is owned by Aurelio De Rosa</small>
