HTML Checking for Large Sites

The button role is used to make an element appear as a button control to a screen reader and can be applied to otherwise non-interactive elements like <div>. If you’re already using a <button> element, then it’s redundant to apply it the role button, as that’s implicit.

<!-- Instead of this -->
<button role="button">Buy</button>

<!-- Do this -->
<button>Buy</button>

The button role is used to make an element appear as a button control to a screen reader and can be applied to otherwise non-interactive elements like <div>. If you’re already using an <input> element whose type is submit, then it’s redundant to apply it the role button, as that’s implicit.

<!-- Instead of this -->
<input type="submit" role="button">Buy</button>

<!-- Do this -->
<input type="submit">Buy</button>

The <summary> HTML element specifies a clickable summary, caption, or legend for a <details> element’s disclosure box. As the <summary> element has an implicit button role, it’s not needed to include it explicitly.

Here’s an example, clicking the <summary> element toggles the state of the parent <details> element open and closed.

<details>
    <summary>I have keys but no doors. I have space but no room. You can enter but can’t leave. What am I?</summary>
    A keyboard.
</details>

A button element is not allowed to contain other button elements, or other elements with role=button.

The button role identifies an element as a button to assistive technology such as screen readers. A button is a widget used to perform actions such as submitting a form, opening a dialog, canceling an action, or performing a command such as inserting a new record or displaying information. Adding role="button" tells assistive technology that the element is a button but provides no button functionality

There can only be one visible <main> element in a document. If more are needed (for example for switching between them with JavaScript), only one can be visible, the others should be hidden toggling the hidden attribute.

Example of 2 main elements, where only one is visible:

<main>
  <h1>Active main element</h1>
  <!-- content -->
</main>

<main hidden>
  <h1>Hidden main element</h1>
  <!-- content -->
</main>

Elements with the role tab must either be a child of an element with the tablist role, or have their id part of the aria-owns property of a tablist.

An element with the tab role controls the visibility of an associated element with the tabpanel role. The common user experience pattern is a group of visual tabs above, or to the side of, a content area, and selecting a different tab changes the content and makes the selected tab more prominent than the other tabs.

Example:

<div class="tabs">
  <div role="tablist" aria-label="Sample Tabs">
    <button role="tab" aria-selected="true" aria-controls="panel-1" id="tab-1" tabindex="0">
          First Tab
    </button>
    <button role="tab" aria-selected="false" aria-controls="panel-2" id="tab-2" tabindex="-1">
          Second Tab
     </button>
  </div>
  <div id="panel-1" role="tabpanel" tabindex="0" aria-labelledby="tab-1">
    <p>Content for the first panel</p>
  </div>
  <div id="panel-2" role="tabpanel" tabindex="0" aria-labelledby="tab-2" hidden>
    <p>Content for the second panel</p>
  </div>
</div>

A button element, or an element with the role=button attribute, is not allowed to be nested inside an <a> element.

A button element cannot contain a descendant element with the attribute tabindex.

labelledby is not a valid attribute for the <svg> element. Perhaps you meant aria-labelledby?

The aria-labelledby attribute establishes relationships between objects and their label(s), and its value should be one or more element IDs, which refer to elements that have the text needed for labeling.

Example:

<div id="myBillingId">Billing</div>

<div>
    <div id="myNameId">Name</div>
    <input type="text" aria-labelledby="myBillingId myNameId"/>
</div>
<div>
    <div id="myAddressId">Address</div>
    <input type="text" aria-labelledby="myBillingId myAddressId"/>
</div>

Due to an issue in the W3C validator, this is identified as an error but it’s not. This issue has been notified, and we’ll update our validator as soon as there’s a fix.

According to the WAI-ARIA 1.2 spec:

The aria-setsize property defines the number of items in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM.

Authors MUST set the value of aria-setsize to an integer equal to the number of items in the set. If the total number of items is unknown, authors SHOULD set the value of aria-setsize to -1.