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目标: 学习可访问性,了解其重要性




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可访问性: 一般原则

We might associate accessibility at first with negative limitations. This building has to be accessible, so it must follow these regulations for door width and toilet size and elevator placement.

That's a narrow way to think of accessibility. Think of it as a wonderful way to empower people and serve more customers. What can the people in Brazil do with your English website? Can the people with smartphones browse a heavy, cluttered website designed for a large desktop monitor and unlimited bandwidth? They'll go somewhere else. In general, we must think about our product from the viewpoints of all our target customers, and adapt accordingly. Hence accessibility.


In the specific context of the web, accessibility means that anyone can benefit from your content, regardless of disability, location, technical limitations, or other circumstances.

Let's consider video:

How does a hearing-impaired person benefit from a video? You have to provide subtitles —or even better, a full text transcript.
Also, make sure people can adjust the volume to accommodate their unique needs.
Again, provide a text transcript that a user can consult without needing to play the video, and an audio-description (an off-screen voice that describes what is happening in the video).
Users may have trouble understanding someone in a video. Let them pause the video to read the subtitles or process the information.
Let the user tab into/out of a video, play it, and pause it without being trapped in it.


A few necessities for basic Web accessibility include:

  • Whenever your site needs an image to convey meaning, include text as an alternative for visually-challenged users or those with slow connections.
  • Make sure all users can operate graphical interfaces (like unfolding menus) solely with a keyboard (e.g., with Tab and the Return key).
  • Provide an attribute explicitly specifying your content's language, so that screen readers read your text properly.
  • Make sure that a user can navigate to all widgets on a page solely with the keyboard, without getting trapped. (At least let them Tab in and out.)



Since 1999, the W3C has operated a working group called the Web Accessibility Initiative (WAI) promoting accessibility through guidelines, support material, and international resources.




Accessibility can impact both a website's design and technical structure.


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