[Markdown] [Glossary] Convert Glossary to markdown - DO NOT SQUASH MERGE

files/en-us/glossary/404/index.md

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+---
+title: '404'
+slug: Glossary/404
+tags:
+  - Glossary
+  - HTTP Errors
+  - Infrastructure
+  - Navigation
+---
+A 404 is a Standard Response Code meaning that the {{Glossary("Server", "server")}} cannot find the requested resource.
+
+## See also
+
+- [list of HTTP response codes](/en-US/docs/Web/HTTP/Status)
+- [advice for beginners on avoiding 404 errors](/en-US/docs/Learn/Common_questions/Checking_that_your_web_site_is_working_properly)

files/en-us/glossary/502/index.md

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+---
+title: '502'
+slug: Glossary/502
+tags:
+  - '502'
+  - Bad Gateway
+  - Glossary
+  - HTTP Errors
+  - Infrastructure
+  - Navigation
+---
+An {{Glossary("HTTP")}} error code meaning "Bad Gateway".
+
+A {{Glossary("Server", "server")}} can act as a gateway or proxy (go-between) between a client (like your Web browser) and another, upstream server. When you request to access a {{Glossary("URL")}}, the gateway server can relay your request to the upstream server. "502" means that the upstream server has returned an invalid response.
+
+Normally the upstream server is not down (i.e. furnishes no response to the gateway/proxy), but does not understand the same data-exchange protocol as the gateway/proxy. Internet {{Glossary("Protocol", "protocols")}} are quite explicit, and so a 502 usually means that one or both machines were incorrectly or incompletely programmed.
+
+## See also
+
+- [list of HTTP response codes](/en-US/docs/Web/HTTP/Status)

files/en-us/glossary/abstraction/index.md

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+---
+title: Abstraction
+slug: Glossary/Abstraction
+tags:
+  - Abstraction
+  - Coding
+  - CodingScripting
+  - Glossary
+  - Programming Language
+---
+Abstraction in {{Glossary("computer programming")}} is a way to reduce complexity and allow efficient design and implementation in complex software systems. It hides the technical complexity of systems behind simpler {{Glossary("API", "APIs")}}.
+
+## Advantages of Data Abstraction
+
+- Helps the user to avoid writing low level code.
+- Avoids code duplication and increases reusability.
+- Can change internal implementation of class independently without affecting the user.
+- Helps to increase security of an application or program as only important details are provided to the user.
+
+## Example
+
+```js
+class ImplementAbstraction {
+  // method to set values of internal members
+  set(x, y) {
+    this.a = x;
+    this.b = y;
+  }
+
+  display() {
+    console.log('a = ' + this.a);
+    console.log('b = ' + this.b);
+  }
+}
+
+const obj = new ImplementAbstraction();
+obj.set(10, 20);
+obj.display();
+// a = 10
+// b = 20
+```
+
+## See also
+
+- {{interwiki("wikipedia", "Abstraction (computer science)", "Abstraction")}} on Wikipedia

files/en-us/glossary/accent/index.md

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+---
+title: accent
+slug: Glossary/accent
+tags:
+  - Glossary
+  - Input
+  - accent
+---
+An **accent** is a typically bright color that contrasts with the more utilitarian background and foreground colors within a color scheme. These are present in the visual style of many platforms (though not all).
+
+On the web, an accent is sometimes used in {{HTMLElement("input")}} elements for the active portion of the control, for instance the background of a checked [checkbox](/en-US/docs/Web/HTML/Element/input/checkbox).
+
+## See also
+
+### CSS related to the accent
+
+You can set the color of the accent for a given element by setting the element's CSS {{cssxref("accent-color")}} property to the appropriate {{cssxref("<color>")}} value.
+
+### HTML elements that may have an accent
+
+- [`<input type="checkbox">`](/en-US/docs/Web/HTML/Element/input/checkbox)
+- [`<input type="radio">`](/en-US/docs/Web/HTML/Element/input/radio)
+- [`<input type="range">`](/en-US/docs/Web/HTML/Element/input/range)

files/en-us/glossary/accessibility/index.md

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+---
+title: Accessibility
+slug: Glossary/Accessibility
+tags:
+  - Accessibility
+  - Glossary
+---
+_Web Accessibility_ (**A11Y**) refers to best practices for keeping a website usable despite physical and technical restrictions. Web accessibility is formally defined and discussed at the {{Glossary("W3C")}} through the {{Glossary("WAI","Web Accessibility Initiative")}} (WAI).
+
+## See also
+
+- [Accessibility resources at MDN](/en-US/docs/Web/Accessibility)
+- {{Interwiki("wikipedia", "Web accessibility")}} on Wikipedia
+- [Learn accessibility on MDN](/en-US/docs/Learn/Accessibility)
+- [Web Accessibility In Mind](https://webaim.org/)
+- [The ARIA documentation on MDN](/en-US/docs/Web/Accessibility/ARIA)
+- [The Web Accessibility Initiative homepage](https://www.w3.org/WAI/)
+- [The WAI-ARIA recommendation](https://www.w3.org/TR/wai-aria/)

files/en-us/glossary/accessibility_tree/index.md

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+---
+title: Accessibility tree
+slug: Glossary/Accessibility_tree
+tags:
+  - AOM
+  - Accessibility
+  - DOM
+  - Glossary
+  - Reference
+---
+The **accessibility tree** contains {{Glossary("accessibility")}}-related information for most HTML elements.
+
+Browsers convert markup into an internal representation called the _[DOM tree](/en-US/docs/Web/API/Document_object_model/How_to_create_a_DOM_tree)_. The DOM tree contains objects representing all the markup’s elements, attributes, and text nodes. Browsers then create an accessibility tree based on the DOM tree, which is used by platform-specific Accessibility APIs to provide a representation that can be understood by assistive technologies, such as screen readers.
+
+There are four things in an accessibility tree object:
+
+- **name**
+  - : How can we refer to this thing? For instance, a link with the text "Read more" will have "Read more" as its name (find more on how names are computed in the [Accessible Name and Description Computation spec](https://www.w3.org/TR/accname-1.1/)).
+- **description**
+  - : How do we describe this thing, if we want to provide more description beyond the name? The description of a table could explain what kind of information the table contains.
+- **role**
+  - : What kind of thing is it? For example, is it a button, a nav bar, or a list of items?
+- **state**
+  - : Does it have a state? Examples include checked or unchecked for checkboxes, and collapsed or expanded for the [`<summary>`](/en-US/docs/Web/HTML/Element/summary) element.
+
+Additionally, the accessibility tree often contains information on what can be done with an element: a link can be _followed_, a text input can be _typed into_, etc.
+
+While still in draft form within the Web Incubator Community Group, the **[Accessibility Object Model](https://wicg.github.io/aom/explainer.html) (AOM)** intends to incubate APIs that make it easier to express accessibility semantics and potentially allow read access to the computed accessibility tree.
+
+## See also
+
+- [Glossary](/en-US/docs/Glossary)
+
+  - {{Glossary("Accessibility")}}
+  - {{Glossary("ARIA")}}

files/en-us/glossary/adobe_flash/index.md

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+---
+title: Adobe Flash
+slug: Glossary/Adobe_Flash
+tags:
+  - Adobe
+  - CodingScripting
+  - Flash
+  - Glossary
+  - Infrastructure
+---
+Flash is a deprecated technology developed by Adobe for viewing expressive web applications, multimedia content, and streaming media. Adobe Flash can run from supporting {{Glossary("Browser","web browsers")}} via a browser plug-in.
+
+## See also
+
+- [Official web site](https://www.adobe.com/products/flashruntimes.html)
+- [Shumway, a free implementation by Mozilla](https://mozilla.github.io/shumway/)
+- [Gnash, a free implementation by GNU](http://gnashdev.org/)
+- [Ruffle, a free implementation](https://ruffle.rs)
+- [Glossary](/en-US/docs/Glossary)
+
+  1.  {{Glossary("Browser")}}
+
+- {{Interwiki("wikipedia", "Adobe Flash")}} (Wikipedia)