The words in the tag should be more than a description. They should provide a text equivalent of the image. In other words, the tag should include the same meaningful information that other users obtain by looking at the image. In the example of the mayor’s picture, adding an “alt” tag with the words “Photograph of Mayor Jane Smith” provides a meaningful description.
The Americans with Disabilities Act (ADA) was first passed in 1990. Twenty years later, the US Department of Justice released an update called the 2010 ADA Standards for Accessible Design. These standards cover the design of physical spaces and have been interpreted to include web locations as well, so it can be difficult for the would-be accessible website designer to use them.
In some circumstances, longer and more detailed text will be necessary to convey the same meaningful information that other visitors to the website can see. For example, a map showing the locations of neighborhood branches of a city library needs a tag with much more information in text format. In that instance, where the map conveys the locations of several facilities, add a “longdesc” tag that includes a text equivalent description of each location shown on the map – e.g., “City Center Library, 433 N. Main Street, located on North Main Street between 4th Avenue and 5th Avenue.”
Because the ADA does not specifically mention websites, it also does not outline standards for how organizations can make their websites accessible. However, the DOJ has frequently cited recommendations such as the Web Content Accessibility Guidelines (WCAG) 2.0 as acceptable metrics for accessibility. WCAG 2.0 includes many different criteria at three different “success levels” of accessibility, ranging from high-contrast color schemes to closed captions for video content.
Many government services and activities are also provided on websites because the public is able to participate in them at any time of day and without the assistance of government personnel. Many government websites offer a low cost, quick, and convenient way of filing tax returns, paying bills, renewing licenses, signing up for programs, applying for permits or funding, submitting job applications, and performing a wide variety of other activities.