Structure

Headings are not only for styling. People with disabilities skim all the headings first to learn what the page is about. It's essential to have headings in right order.

Nest headings by their rank (or level). The most important heading has the rank 1 (<h1>), the least important heading rank 6 (<h6>). Headings with an equal or higher rank start a new section, headings with a lower rank start new subsections that are part of the higher ranked section.

Skipping heading ranks can be confusing and should be avoided where possible: Make sure that a <h2> is not followed directly by an <h4>, for example. It is ok to skip ranks when closing subsections, for instance, a <h2> beginning a new section, can follow an <h4> as it closes the previous section.

Link texts

Write link text so that it describes the content of the link target. Avoid using ambiguous link text, such as ‘click here’ or ‘read more’. Indicate relevant information about the link target, such as document type and size, for example, ‘Proposal Documents (RTF, 20MB)’.

Read more about the engineering program.
For more information on the engineering program, click here.

Bold and Italic tags

The Bold tag, <b>, and the italic tag, <i>, are listed as a WCAG Level A error because most screen readers will NOT announce these changes to the screen reader user. <b> and <i> should not be used to style text when the author wants to emphasize a word or passage of text.

Bold

<strong>bold text</strong>
<b>bold text</b>

Italic

Sometimes plugins and forms use <i> tags. If they're not used to format the text styles, you can ignore the issues on Siteimprove.

<em>Italic text</em>
<i>Italic text</i>

Underline

In general, text should not be underlined unless it is used as a hyperlink. This does not mean that underlined text is inherently bad. It just means that the convention on the web is to underline links. People have gotten used to this convention. Using underlined text for non-link purposes on the web will likely confuse some users, who may attempt to click on the underlined terms.

Centering

<center> is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

<div style="text-align:center">This text will be centered.</div>
<center>This text will be centered.</center>

Updated

Strikethrough

<s> and <strike> are obsolete. Even with the active tag <del>, screen readers cannot convey any information regarding the tags. Try not to use it as much as you can. If you have to use it, you need to work around with CSS.

<del>Deleted text</del>

del::before,
del::after {
  clip-path: inset(100%);
  clip: rect(1px, 1px, 1px, 1px);
  height: 1px;
  overflow: hidden;
  position: absolute;
  white-space: nowrap;
  width: 1px;
}
del::before {
  content: " [deletion start] ";
}
del::after {
  content: " [deletion end] ";
}
<s>Deleted text</s>
<strike>Deleted text</strike>