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Appendix C. Glossary


A technology developed by Microsoft to allow components to be created, primarily for Windows computers. ActiveX components, or controls, can be embedded in Web pages.


In HTML, a named location within a document, specified using the <a> tag. Anchors can also act as links.


A Java program that is designed to be embedded in a Web page.


A parameter that is passed to a function when it is called. Arguments are specified within parentheses in the function call.


A set of variables that can be referred to with the same name and a number, called an index.


A property value that can be defined within an HTML tag. Attributes specify style, alignment, and other aspects of the element defined by the tag.


A type of variable that can store only two values: true and false.

browser sensing

A scripting technique that detects the specific browser in use by clients to provide compatibility for multiple browsers.

Cascading Style Sheets (CSS)

The W3C's standard for applying styles to HTML documents. CSS can control fonts, colors, margins, borders, and positioning.


The act of combining two strings into a single, longer string.


A JavaScript statement that performs an action if a particular condition is true, usually using the if statement.


To decrease the value of a variable by one. In JavaScript, this can be done with the decrement operator, --.


The act of finding errors, or bugs, in a program or script.


A term the W3C applies to HTML tags or other items that are no longer recommended for use, and may not be supported in the future. For example, the <font> tag is deprecated in HTML 4.0, since style sheets can provide the same capability.

Document Object Model (DOM)

The set of objects that JavaScript can use to refer to the browser window and portions of the HTML document. The W3C (World Wide Web Consortium) DOM is a standardized version supported by the latest browsers, and allows access to every object within a Web page.

Dynamic HTML (DHTML)

The combination of HTML, JavaScript, CSS, and the DOM, which allows dynamic Web pages to be created. DHTML is not a W3C standard or a version of HTML.


A single member of an array, referred to with an index. In the DOM, an element is a single node defined by an HTML tag.


A condition, often the result of a user's action, that can be detected by a script.

event handler

A JavaScript statement or function that will be executed when an event occurs.


A combination of variables, constants, and operators that can be evaluated to a single value.

feature sensing

A scripting technique that detects whether a feature, such as a DOM method, is supported before using it to avoid browser incompatibilities.


A group of JavaScript statements that can be referred to using a function name and arguments.

global variable

A variable that is available to all JavaScript code in a Web page. It is declared (first used) outside any function.

Hypertext Markup Language (HTML)

The language used in Web documents. JavaScript statements are not HTML, but can be included within an HTML document.


To increase the value of a variable by one. In JavaScript, this is done with the increment operator, ++.


The browser component that interprets JavaScript statements and acts on them.


An object-oriented language developed by Sun Microsystems. Java applets can be embedded within a Web page. JavaScript has similar syntax, but is not the same as Java.


A scripting language for Web documents, loosely based on Java's syntax, developed by Netscape. JavaScript is now supported by the most popular browsers.


An area of a Web page that can be positioned and can overlap other sections in defined ways. Layers are also known as positionable elements.

local variable

A variable that is available to only one function. It is declared (first used) within the function.


A set of JavaScript statements that are executed a number of times, or until a certain condition is met.


A specialized type of function that can be stored in an object, and acts on the object's properties.


A browser developed by Netscape, and the first to support JavaScript.


In the DOM, an individual container or element within a Web document. Each HTML tag defines a node.


A type of variable that can store multiple values, called properties, and functions, called methods.


A character used to divide variables or constants used in an expression.


A variable sent to a function when it is called, also known as an argument.


A variable that is stored as part of an object. Each object can have any number of properties.


In CSS, an individual element of a style block that specifies the style for an HTML tag, class, or identifier.


The part of a JavaScript program that a variable was declared in and is available to.


In a CSS rule, the first portion of the rule that specifies the HTML tag, class, or identifier that the rule will affect.


A single line of a script or program.


A group of text characters that can be stored in a variable.


In HTML, an individual element within a Web document. HTML tags are contained within angle brackets, as in <body> and <p>.

text node

In the DOM, a node that stores a text value rather than an HTML element. Nodes that contain text, such as paragraphs, have a text node as a child node.


A container, referred to with a name, that can store a number, a string, or an object.


A scripting language developed by Microsoft, with syntax based on Visual Basic. VBScript is supported only by Microsoft Internet Explorer.

World Wide Web Consortium (W3C)

An international organization that develops and maintains the standards for HTML, CSS, and other key Web technologies.

XHTML (Extensible Hypertext Markup Language)

A new version of HTML developed by the W3C. XHTML is similar to HTML, but conforms to the XML specification.

XML (Extensible Markup Language)

A generic language developed by the W3C (World Wide Web Consortium) that allows the creation of standardized HTML-like languages, using a DTD (Document Type Definition) to specify tags and attributes.



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