Absent qualifying descriptors, web accessibility refers to the degree to which a website's content is accessible to those who, because of some form of physical impairment (most commonly, blindness), can not access web content in its most typical, visual form. These users often access web content via screen readers or other translation software which literally reads the web content aloud to the user. If a website has not been built with accessibility in mind, screen readers, etc. will not be able to access content. Common practices that web authors use that detract from accessibility (web barriers) include use of tables (as opposed to CSS positioning), Javascript rollover buttons, Flash-based navigation and embedding text inside image files (jpg, gif, etc.). For most of these techniques there are "work-arounds" that make content accessible, but those practices often go unused.

Inaccessibility can also refer to websites that require software that some users do not possess. Most commonly, web authors use newer versions of specific software (e.g. Flash, Adobe PDF), that require users to have the latest "reader" application. In absence of an appropriate reader, users cannot access the content.

Community content is available under CC-BY-SA unless otherwise noted.