On your webpage, you click a link that skips the user to the main content of the website. These are often referred to as skip links, or anchor links. When that link is activated by a keyboard, using the tab and enter keys, the main content container has a focus ring around it. Why is that?

This is because the <main> has a tabindex="-1" attribute value, which means it can be programmatically focused. When the <main> is targeted—because the #main-content in the browser URL bar matches the id—it receives programmatic focus. It's tempting to remove the focus styles in these situations, but handling focus appropriately and with care helps to create a good, accessible, user experience. It can also be a great place to add some interest to interactions.

Why is focus important?

As a web developer, it's your job to make a website accessible and inclusive to all. Creating accessible focus states with CSS is a part of this responsibility.

Focus styles assist people who use a device such as a keyboard or a switch control to navigate and interact with a website. If an element receives focus and there is no visual indication, a user may lose track of what is in focus. This can create navigation issues and result in unwanted behaviour if, say, the wrong link is followed.

How elements get focus

Certain elements are automatically focusable; these are elements that accept interaction and input, such as <a>, <button>, <input> and <select>. In short, all form elements, buttons and links. You can typically navigate a website's focusable elements using the tab key to move forward on the page, and shift + tab to move backward.

There is also a HTML attribute called tabindex which allows you to change the tabbing index—which is the order in which elements are focused—every time someone presses their tab key, or focus is shifted with a hash change in the URL or by a JavaScript event. If tabindex on a HTML element is set to 0, it can receive focus via the tab key and it will honour the global tab index, which is defined by the document source order.

If you set tabindex to -1, it can only receive focus programmatically, which means only when a JavaScript event happens or a hash change (matching the element's id in the URL) occurs. If you set tabindex to be anything higher than 0, it will be removed from the global tab index, defined by document source order. Tabbing order will now be defined by the value of tabindex, so an element with tabindex="1" will receive focus before an element with tabindex="2", for example.

Styling focus

The default browser behavior when an element receives focus is to present a focus ring. This focus ring varies between both browser and operating systems.

This behavior can be changed with CSS, using the :focus, :focus-within and :focus-visible pseudo-classes that you learned about in the pseudo-classes lesson. It is important to set a focus style which has contrast with the default style of an element. For example, a common approach is to utilize the outline property.

a:focus {
                                  outline: 2px solid slateblue;
                                }
                                

The outline property could appear too close to the text of a link, but the outline-offset property can help with that, as it adds extra visual padding without affecting the geometric size that the element fills. A positive number value for outline-offset will push the outline outwards, a negative value will pull the outline inwards.

Currently in some browsers, if you have a border-radius set on your element and use outline, it won't match—the outline will have sharp corners. Due to this, it is tempting to use a box-shadow with a small blur radius because box-shadow clips to the shape, honouring border-radius, but this style will not show in Windows High Contrast Mode. This is because Windows High Contrast Mode doesn't apply shadows, and mostly ignores background images to favor the user's preferred settings.

In summary

Creating a focus state that has contrast with an element's default state is incredibly important. The default browser styles do this already for you, but if you want to change this behaviour, remember the following:

• Avoid using outline: none on an element that can receive keyboard focus.
• Avoid replacing outline styles with box-shadow. as they don't show up in Windows High Contrast Mode.
• Only set a positive value for tabindex on an HTML element if you absolutely have to.
• Make sure the focus state is very clear vs the default state.