Accessibility is the degree to which something can be used, accessed or accessed by all persons, regardless of their technical or physical.
The accessibility applied to Internet content is called web accessibility. On the Web, W3C has developed guidelines or specific guidelines to enable and secure this type of-Accessibility. The working group within W3C is in charge of promoting the WAI.
For guidelines published in W3C right here: https://www.w3.org/TR/2000/NOTE-WCAG10-HTML-TECHS-20001106
Web accessibility indicates the ability to access the web and its contents to all persons regardless of disability (physical, intellectual or technical) they have or those resulting from the use context (technological or environmental).
On the web have defined access keys in each of its component sections. The key combination to access the main sections of the device depend on platform and web access. One of the most common cases are the key combination [alt] + [access key or ctrl] + [accesskey]