Guideline 1.3: Adaptable - Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
Success Criterion 1.3.1: Info and Relationships - Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.
What is Semantic Structure or Semantic Markup? As the Siteimprove article Guide to Accessible Semantic Markup puts it, "semantic markup is a fancy term for common-sense HTML usage." [1]
You may be thinking, unless I edit my LibGuides with an HTML editor, I shouldn't have to concern myself too much with semantic HTML markup. However, the rules that govern the code are applied to the LibGuide text editor. So, whether you are editing in code or the text editor, it's good to follow a semantic structure. For instance, if we look at the text editor, we will find a Link icon (which marks your content with an <a> tag) and Header and Paragraph options under the Paragraph Format drop-down menu (headers mark content with an <h> tag while paragraphs are marked with a <p> tag). If you are using the text editor you may never have to actually see these tags, but it's important to note how the elements you add affect the navigation, usability, and accessibility of your guide.
Why are these options important? Each element that we've discussed, and those that will be reviewed later on this guide, have some basic visual styling applied, but they also offer keyboard accessibility and screen-reader details that are missed (or misused) if not correctly applied. In this guide, we will review some of the basic elements commonly used in LibGuides, and why it's important they are used properly.
Excerpt from W3C: Info and Relationships
Sighted users perceive structure and relationships through various visual cues — headings are often in a larger, bold font separated from paragraphs by blank lines; list items are preceded by a bullet and perhaps indented; paragraphs are separated by a blank line; items that share a common characteristic are organized into tabular rows and columns; form fields may be positioned as groups that share text labels; a different background color may be used to indicate that several items are related to each other; words that have special status are indicated by changing the font family and /or bolding, italicizing, or underlining them; items that share a common characteristic are organized into a table where the relationship of cells sharing the same row or column and the relationship of each cell to its row and/or column header are necessary for understanding; and so on.
When such relationships are perceivable to one set of users, those relationships can be made to be perceivable to all.
Having these structures and these relationships programmatically determined or available in text ensures that information important for comprehension will be perceivable to all. [2]