Consistency is one of the cornerstones of good usability. Although it is possible in advanced CMSs to create radically different page layouts according to content type, it's important that areas outside of the page’s content area remain consistent across the site for wayfinding purposes. This can be controlled through carefully designing and implementing page templates.... Read more about ✎ Technique: Consistent layout

Paragraphs of text are a fundamental core of web content, so it's important to display them in a fashion that is optimally readable to the majority of your audience without requiring them to change their display settings. For people who do need to customize display of text to make it easier to read, it's important to support this customization rather than forcing them to read the text the way you specify.

For the most part, this means applying typesetting best practices, which predate the web.

Some people with reading difficulties or visual impairments need to customize the display of text to make it easier to read. When text is presented as an image of text, that limits their ability to change the appearance of that text. So wherever possible, use text along with CSS to apply styling (such as color, typeface, or size).

If you use an online content editor to write content, the styling will happen automatically. If you feel that you need text that deviates from the style, formatting options...

Some people with color deficit have trouble differentiating between specific colors, such as between red and green or red and black. Screen reader users do not access content visually, so they do not have access to color information.

Color is a powerful visual means of presenting or distinguishing information, but when you use color to identify or distinguish information, make sure that this information is still available to people who can't perceive color.

A clear indication that specific form fields are required can save users time and avoid potential errors relating to missing data when a form is submitted.

This indication should be visually distinct without relying on color, and it should also be programmatically available to screen-reader users.

For a number of reasons including data persistence, performance and security, it is sometimes beneficial to terminate idle user sessions.

So that users do not lose data, it's important to warn them of a session that is about to expire and give them the option to continue. This is especially true in the case of people who might take longer to read or interact with a page due to a disability. It's important to make such prompts accessible.

Some people with reduced visual acuity may not need screen magnification software or screen readers but might still have problems reading smaller fonts. So the ability to allow easy enlargement of text size is important.

There are a number of ways to zoom web-page content in to enlarge text without needing to provide explicit controls to do so. To avoid diminishing this variety of user control, you have to be careful how you code font sizes.

Modal dialogs can enhance usability by focusing attention on a specific message that requires a user action to continue.

An accessible modal dialog is one where keyboard focus is managed properly, and the correct information is exposed to screen readers. HTML and WAI-ARIA can be used to provide the necessary semantic information, CSS the appearance and Javascript the behavior.

Interactive elements should not be difficult to select or activate when using a mouse or a touchscreen.

Generous sizing and spacing is important, and their implied visual “hit area” should correspond to the control’s active area.

All interactive elements should be focusable so that they can be activated using a mouse, a keyboard, voice recognition software, a switch input device, and other input methods.

They should also indicate when they’re focused so that users know which element they are currently interacting with. This is where focus styles come into play.

The heading levels (1-6) are often considered a way of describing and determining the “importance” of a heading, with h1 being the most important. This might be reflected in the visual appearance of headings—higher-level headings typically appear as bigger and bolder text than lower-level headings.

But you can't just put an “important” heading anywhere. Its heading level relates to how much content it refers to, and that has to do with structure.

Reflecting structure accurately allows screen-reader users to use their screen reader's heading-navigation feature to navigate by heading level, building up an idea of document structure. It also ensures that, for people who use custom stylesheets, heading structure is preserved even when the appearance of headings is changed.... Read more about ✎ Technique: Heading structure

For a readable interface, it's important to use visual cues to group or separate content to show which content relates to other content. This makes content easier to read, especially for people who have difficulty reading on-screen content and people who use screen readers.

When grouping content visually, you must make sure that you're not skewing the source order and breaking up the same content for screen-reader users.

When positioning elements using CSS, it's possible to place them in a position that does not reflect their location in the source order. This can have unexpected side effects for keyboard-navigation users.

The most appropriate alternative text for an image depends very much on the context of the image in question. You must provide information for that image that takes into account its purpose and also the surrounding text on the page. The same image might need different alternative text depending on how it's used.... Read more about ✎ Technique: Writing alternative text

Each image requires alternative text that is equivalent to the information it conveys, unless the image is purely decorative and provides no useful information. So you need to be careful about what value you give the alt attribute.