According to the U.S. Census Bureau report "Americans with Disabilities, 1997",  52.6 million people (19.7 percent of the population) had some level of disability and 33.0 million (12.3 percent of the population) had a severe disability.  This makes people with disabilities the largest minority in the United States!

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The vision impaired can encounter barriers on the web including:

• Images with no "alternative text"
• complex images not adequately described
• video that isn't described in text or audio
• tables that make no sense when read in a "cell by cell" manner 

For the hearing impaired, barriers include:

• lack of captions or transcripts of audio on the Web
• lack of content-related images in pages full of text, which can slow comprehension for people whose first language may be a sign language

For the mobility impaired, barriers may include:

• time-limited response options on Web pages
• browsers that don't support keyboard alternatives for mouse commands
• formats that can't be tabbed through in a logical order

For the cognitive and neurological disabled, barriers include:

• lack of alternative modalities for information on Web sites, for instance lack of alternative text that can be converted to audio to supplement visuals, or the lack of captions for audio
• distracting visual or audio elements that cannot easily be turned off
• use of unnecessarily complex language on Web sites
• lack of graphics on Web sites - some people may rely more on graphics to enhance understanding of a site or to assist in understanding of page content
• lack of clear or consistent organization of Web sites