Web accessibility refers to making web pages available and readable to all users, including those with disabilities such as sight or hearing impairments. An estimated 20% of the population in the United States (40.8 million) has some kind of disability. To understand why web accessibility is so important, it may be helpful to first understand how people with disabilities use the Internet, and how their disability affects their use of the Internet. The following five general types of disabilities affect Internet usage:
- Visual impairments - unlabeled graphics, screen reader incompatibilities.
- Hearing impairments - lack of captions for audio content, auditory prompts without visual signposts
- Mobility impairments - lack of alternatives for input/navigation (e.g., voice recognition or eye-gaze)
- Cognitive impairments - inconsistent navigational structures, distracting graphics and text movement
- Seizure disorders - blinking or flashing items can trigger seizures (in the 4 to 59 flashes per second/Hertz range)
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How a blind person will "see" your Web page - audio comparison of inaccessible and accessible web pages (from Human Factors International)
How to Create Accessible Tables - (from WebAIM)
- Although HTML tables were designed for data layout, tables are more commonly used for page layout.
- Complex table layouts, with many columns and rows can be disorienting to a user when listening to a screen reader (or when feeling the Braille output), especially if the visual reading order differs from the structural reading order.
- The structural reading order of a table starts with the first row, first column, left to right, one column at a time, until reaching the last cell on the bottom right of the table.
- Even though the original purpose of tables was for data display, data tables still can be confusing to screen readers.
How to Create Accessible Forms - (from accessify.com) shows how to make accessible forms using css or table layouts.
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What is WebXACT (formerly known as Bobby)?
WebXACT is a tool for analyzing your web page(s) for accessibility. It was developed by the Center for Applied Special Technology (CAST) and is available for free on the web. This tool can analyze single pages or can be downloaded and applied to a directory of files.
Access WebXACT at: http://webxact.watchfire.com/
What are the different conformance levels and how do they relate to Bobby?
There are three levels of conformance (standards established by the WAI - Web Accessibility Initiative, http://webaim.org) that correspond to Bobby's Priority level checkpoints (Priority 1 is the most important):
- Conformance Level "A" = Priority 1 checkpoints must be satisfied
- Conformance Level "Double-A" = Priority 2 checkpoints should be satisfied
- Conformance Level "Triple-A" = Priority 3 checkpoints may be satisfied
How can I simulate a screen reader to check my web pages?
Download Lynx, a browser that views web pages in text-mode and illustrates what a screen reader has to read.
Lynx is available at: http://lynx.browser.org/
Are PDF (Adobe's Portable Document Format) files accessible?
If you are using PDF files, you should provide an HTML alternative. You should also provide a link to Adobe's website where users can download plug-ins (software tools) that convert PDF files to text format for delivery by nonvisual browsers (Adobe's plug-in is available at: http://access.adobe.com).
What do I need to do to make PowerPoint files accessible?
If you choose to post the original slides, you should also post the same content in an HTML format in order to accommodate those using screen reader technologies. PowerPoint 2000 has an export feature that does a good job of saving content as real text. Be sure to include text descriptions of any graphics used as these will not render as web accessible.
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For a thorough list of guidelines for accessible HTML authoring, visit the W3C's web page at:
http://www.w3.org/TR/WAI-WEBCONTENT/
Additional Resources:
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