This technique relates to the following sections of the guidelines:
If the non-text content does not provide functionality or convey information, then mark the non-text content so that it may be ignored. Ask, "Will it be distracting? Is the non-text content necessary to understand the rest of the content? Is there another way to create the effect?"
Where users might want to be made aware that such content is present, use techniques for other success criteria for guideline 1.1. In most cases, users find it distracting to know about individual units of non-text content that do not convey information or provide functionality. For example, “spacer” images - transparent images used to control the layout of content - are not visible to most users. However, screen readers will read text alternatives associated with spacer images, which is distracting and oftentimes confusing. The same is true for many decorative graphics that are used to enhance readability by breaking up large blocks of text or simply to enhance the visual appearance of the page. To avoid these distractions, either:
Mark decorative non-text content in such a way that a user agent can ignore it or
Create decorative effects with more accessible methods.