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absolute positioning

Setting the precise location of an element within the coordinate system of the next outermost container. An absolute-positioned element exists in its own transparent layer; it is removed from the flow of content that surrounds it in the HTML source code.


The design concern for allowing users with physical disabilities to make as full a use of web content as possible. For example, aural style sheets provide increased web accessibility to users who have vision impairments.


Application Programming Interface, which is usually a collection of methods and properties that operate as a convenient layer between programmers and more complex internal computer activity. In Dynamic HTML, it is common to use or create a custom API to act as a buffer between the browser-specific implementations of element positioning and the programmer's desire to use a single coding scheme regardless of browser.


A type of CSS command used inside a style sheet definition. Typical at-rule commands import external style sheets or download font specifications. An at-rule statement begins with the @ symbol.


A property of an HTML element or CSS style sheet. Attributes are usually assigned values by way of operators (the = symbol for HTML; the : symbol for CSS). In HTML, sometimes the presence of the attribute name is enough to turn on a feature associated with that attribute. HTML attribute names are case insensitive; CSS attribute names are case sensitive.

block-level element

An HTML element that automatically forces a new line before and after the element, assuring that no other element appears in the same horizontal band of the page (unless another element is absolute-positioned on top of it). An example of a block-level element is the H1 element.


In CSS, a region that exists outside of the content and padding area of a block-level element. The border is always present, even if its thickness is zero, and it can't be seen. A border is sandwiched between the margin and padding.

cascading rule

One of the sequence of decisions that a CSS-equipped browser uses to determine which one of possibly several overlapping style sheet rules applies to a given element. Each cascading rule assigns a value to a specificity rating that helps determine which style sheet rule applies to the element.


In CSS, a collection of one or more elements (of the same or different tag type) that are grouped together for the purpose of assigning the same style sheet rule throughout the document. Assigning a class identifier to elements via the CLASS attribute (and using that class selector in a style sheet rule) lets authors create element groupings that cannot be created only out of tag names or IDs.


Microsoft's terminology for an array of scriptable objects. To reference an item of a collection in a script statement in Internet Explorer 4, you may use either array notation (collectionName[index]) or collection notation (collectionName(index)).


Any element that holds other elements of any type. Tags for contained elements appear between the container's start and end tags.

contextual selector

In CSS, a way of specifying under what containment circumstances a particular type of element should have a style sheet rule applied to it. The containment hierarchy is denoted in the selector by a space-delimited list. Thus, the rule P EM {color: red} applies the red text color to all EM elements that are contained by P elements; an EM element inside an LI element is unaffected by this style sheet rule.


Acronym for Cascading Style Sheets, a recommended standard created under the auspices of the World Wide Web Consortium (W3C). The acronym is commonly followed by a number designating the version number of the standard. Level 1 of CSS is known as CSS1.


Acronym for Cascading Style Sheets-Positioning. Initially undertaken as an effort separate from the CSS work, the two standards come together in CSS2.

data binding

A facility in Microsoft Internet Explorer 4 for Win32 platforms that allows web page content to be dynamically linked to a data source, such as a server database. For example, a MARQUEE element can grab the latest headlines from a database field as the page loads into the client and display those headlines as a scrolling tickertape.


In CSS, the combination of an attribute name, colon operator, and value assigned to the attribute. Multiple declarations in a single style sheet rule are separated by semicolons.


In web standards, a feature (commonly an HTML element or attribute) that is still supported in a standards release version, but whose use is discouraged in documents that support the version. A term that is deprecated in one version release is usually removed in the following release. Browser support for deprecated items usually continues for many generations for backward compatibility with existing documents that use the element or attribute.


Acronym for Dynamic Hypertext Markup Language. DHTML is an amalgam of several standards, including HTML, CSS, and DOM.


Acronym for the Document Object Model standards effort headed by the W3C. The term is commonly applied to a specific implementation of a document object model in a particular browser, but this is not entirely accurate.

dynamic content

Any HTML content that changes after the document has loaded. Content that does not require a reflow of the page can be accommodated in Navigator 3 and onward and Internet Explorer 4 and onward. The replaced IMG element is an example. IE 4 also allows body content to be changed after the document loads by automatically reflowing the page after the content changes.


A Switzerland-based standards body formerly known as the European Computer Manufacturers Association.


The common name for the JavaScript-based scripting language standard ECMA-262. The standard defines a core scripting language, without any specific references to web-based content. The functionality of ECMA-262 is roughly equivalent to JavaScript 1.1 as deployed in Navigator 3.


Refers to an HTML element, which is an item created by an HTML tag in a document. For example, the <BODY> tag creates a BODY element in the document.

event bubbling

The Internet Explorer 4 event model that propagates events from the target element upward through the HTML element hierarchy. After the event is processed (at the scripter's option) by the target element, event handlers further up the hierarchy may perform further processing on the event. Event propagation can be halted at any point via the cancelBubble property.

event handler

A script-oriented keyword that intercepts an event action (such as a mouse click) and initiates the execution of one or more script statements. An event handler can be specified as an attribute of an HTML element or assigned as a property of the scriptable object version of the element. Each element has its own set of events that it recognizes and corresponding event handlers (e.g., an onKeyPress event handler for the keyPress event) to bind to script statements.

event propagation

The process of event information coursing its way through the element or object hierarchy of a document. Navigator 4 events trickle down from the window level toward the target element; Internet Explorer 4 events bubble upward from the target element toward the BODY element. If event processing is to be handled by objects other than the target element (in which case the element's event handler is treated the same way in both browsers), different event scripting is required to accommodate both event propagation schemes within a single document.


A rendering feature of Internet Explorer 4 (for the Win32 platform) that adds typographic effects to text content. A filter is assigned to an element by way of CSS syntax.


Acronym for Hypertext Markup Language, a simplified version of SGML tailored for content that is published across a network via the Hypertext Transfer Protocol (HTTP). Version 4.0 of the HTML standard (under the auspices of the W3C) extends the notion of separating content from form by letting HTML elements define the context of content, rather than its specific look.


An identifier for an HTML element that should be unique among all elements within a single document. The ID of an element is assigned by the ID attribute supported by virtually every HTML 4.0 tag. An ID is used for many purposes but primarily for associating a CSS style sheet rule with a single element among all elements of a document. An element can belong to a class and have a unique ID at the same time.


A name assigned to an ID, CLASS, or NAME attribute of an element. An identifier is also used in script references, especially in Internet Explorer 4. The names can begin with any uppercase or lowercase letter of the English alphabet, but subsequent characters may include letters, numerals, or the underscore character.

inline element

An HTML element that is rendered as part of the same text line as its surrounding HTML content. An EM element that signifies an emphasized portion of a paragraph is an inline element because its content does not disturb the regular linear flow of the content. The opposite of an inline element is a block-level element.

intrinsic events

Event handlers defined by the HTML 4.0 standard as belonging to virtually every element that is rendered on the page. These events are primarily the common mouse and keyboard events.


A programming language devised by Brendan Eich at Netscape for simplified server and client programming. Originally developed under the name LiveScript, the name changed (under license from Sun Microsystems) before the first commercial release of a scriptable browser, Navigator 2. JavaScript became the basis for ECMAScript. Microsoft's name for its implementation of JavaScript is JScript.

JavaScript Style Sheets

A Navigator-only syntax for defining style sheet rules.


Microsoft's formal name for the JavaScript-based scripting language built into Internet Explorer 3 and later. JScript is compatible with ECMAScript and Java-Script.


Navigator's model for a positionable element. A layer can be created via the <LAYER> tag or by associating a CSS-P position:absolute style sheet declaration with an element. Navigator scripts for accessing a positionable element (regardless of how the element is created) refer to the element as a layer object. Although Internet Explorer does not use the layer terminology, each absolute-positioned element exists in its own transparent layer above the main document body.


In CSS, a region that extends outside of an element's border. Every element has a margin, even if its thickness is zero.


A scriptable object's action that can be initiated by any script statement. A reference to a JavaScript method is easily recognizable by the set of parentheses that follows the method name. Zero or more parameters may be included inside the parentheses. A method may return a value depending on what it has been programmed to do, but this is not a requirement.

modifier key

A keyboard key that is usually pressed in concert with a character key to initiate a special action. Modifier keys common to all operating system platforms include the Shift, Control, and Alt keys. Modern Microsoft keyboards also have the Windows key; Macintosh keyboards have the Command key. Keyboard events can be examined for which (if any) modifier keys were being held down at the time of the character key's event.


A representation of an HTML element or other programmable item in a scripting language, such as JavaScript. An object may have properties and methods that define the behavior and/or appearance of the object. Scripts typically read or modify object properties or invoke object methods to affect some change of value or appearance of the object. Objects in a browser's document object model reflect HTML elements defined by the document source code. For example, in recent browser versions, if a script assigns a new URL to the value of the src property of an image object, the new image replaces the old within the rectangular space occupied by the IMG element on the page. Other types of objects, such as dates and strings, do not appear on the screen directly but are used in script execution.


In CSS, a region that extends between the element's content and the border. Padding provides some "breathing space" between the content and a border (if one is specified). Every element has padding, even if its thickness is zero. Navigator 4 automatically adds padding to all elements.


For HTML elements, the next outermost element in source code order (the P element that surrounds an EM element, for example). For positioned elements, the element that is the next outermost container that determines the coordinate plane for the element's positioning. For scriptable window objects, the window or frame that contains a frameset document that defines the frame holding the current document.


A software or hardware system that forms the basis for further product development. For web browsers, the term may apply to a browser brand (Netscape Navigator, Microsoft Internet Explorer, etc.) or the operating system on which a browser brand operates (Windows 95, Windows 3.1, Macintosh, Solaris, etc.). In this book, platform usually applies to the browser brand.


Specifying the precise location of an element on the page. An element may be absolute-positioned or relative-positioned.


A single characteristic of an object, such as its ID or value, which can be retrieved (and sometimes set) with the help of scripting. Style sheet attributes are also sometimes referred to as properties.


A style sheet selector that points to a particular state or behavior of an HTML element, such as an A element set up as a link that has been visited recently by the user (A:visited).


A style sheet selector that points to a very specific piece of an element, such as the first letter of a paragraph (P:first-letter).

relative positioning

Setting the precise location of an element within the coordinate system established by the location where the element would normally appear if it were not positioned. Documents preserve the space originally designated for a relative-positioned element so that surrounding content does not cinch up around the place left vacant by a positioned element.

replaced element

An inline or block-level element that can have its content replaced without requiring any adjustment of the document. An IMG element, for example, can have its content replaced by a script after the page has loaded.


In CSS, a set of style declarations that are associated with one selector. A rule can also be embedded within an element as the value assigned to the STYLE attribute of the element's tag.


In CSS, the name of the element(s), ID(s), class(es), or other permissible element groupings to which a style declaration is bound. The combination of a selector and declaration creates a style sheet rule.

style sheet

In CSS, one or more rules that defines how a particular segment of document content should be rendered by the browser. A style sheet may be defined in an external document, in the STYLE element, or assigned to an element via its STYLE attribute.


In Internet Explorer 4, a visual effect for hiding and showing elements. Transitions are available only in the Win32 version of IE 4.


A scripting language alternate to JScript in Internet Explorer 4. This language is not available in any version of Navigator.



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