- 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.
- abstract object
A specification for the characteristics of other, real objects with
which scripts come into contact. Modern document object model
designers frequently blend the characteristics of multiple abstract
objects into a single scriptable object. For example, the properties,
methods, and event handlers for a specific HTML p
element object in a document loaded into Netscape 6 are derived from
many W3C DOM specification abstract objects: the
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. See also WAI.
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
A property of an HTML (and XHTML) 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
(regardless of the value assigned), but XHTML requires that all
attributes have values assigned to them. HTML attribute names are
case-insensitive; XHTML and 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
- browser sniffing
A script technique (usually involving properties of the
navigator object) that sets global variables
signifying the current browser's brand, version,
operating system, and other environment capabilities. Scripts use the
variables to branch code execution to accommodate browser-specific
syntax for operations to work across multiple, incompatible browsers.
The technique is gradually being displaced by object
- cascading rule
One of the sequence of decisions that a CSS-equipped browser uses to
determine which one of several possible 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 (and
attributes within that 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.
A group of scriptable objects of the same type. Scripts may reference
individual members of the collection via standard numeric array index
aided by the collection's length
property for iterative access inside for loops, if
desired. In recent browsers, methods allow access via numeric index
or, if the objects have names associated with them, their names
Internet Explorer also allows references through its own collection
Many DOM properties and methods return values in the form of a
Any element that holds other elements of any type. Tags for contained
elements appear between the container's start and
- 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
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
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 2 of CSS is known as CSS2.
Acronym for Cascading Style Sheets-Positioning. Initially undertaken
as an effort separate from the CSS work, the two standards come
together in CSS2, and the CSS-P terminology is no longer needed.
- data binding
A facility in Microsoft Internet Explorer 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. Windows
versions have two-way access to many data source types, but IE for
Macintosh's data binding works only with static tab-
or comma-delimited text file sources.
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.
A web standard or language feature (commonly an HTML element or
attribute and corresponding DOM equivalent) that is still supported
in a standards release version, the use of which 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 (and XHTML), CSS, and DOM.
Acronym for the Document Object Model standards effort headed by the
W3C. The term in all uppercase letters is commonly, but perhaps
inappropriately, applied to a specific implementation of a document
object model in a particular browser.
Acronym for the Document Type Definition, a document that defines in
excruciating detail the types of elements, attributes, and attribute
values that are permissible in an SGML (and thus HTML or XML)
document. Users never see DTD documents, but they are commonly
referenced within the <!DOCTYPE> element at
the top of a document to define the markup rules followed by the
document's content. Anyone may create a custom DTD
for their documents, but most HTML documents adhere to one of the
- 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 or later
and Netscape 6 also allow body content to be changed after the
document loads by automatically reflowing the page after the content
A Switzerland-based standards body formerly known as the European
Computer Manufacturers Association.
ECMA-262. The standard defines a core scripting language, without any
specific references to web-based content. The functionality of the
deployed in Navigator 3. The second edition corrected errors of the
Refers to a portion of a document that has a specific context within
the document defined by an angle-bracketed tag or tag pair (start and
end tag set). For example, the <body> tag
creates a body element in the document.
- event binding
A technique of instructing an object to process a particular event
type when the event fires on that object.
- event bubbling
The Internet Explorer 4 or later and Netscape 6 event model mechanism
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 higher up the hierarchy may perform further processing on
the event. Event propagation can be halted at any point via the
cancelBubble property or, in Netscape 6, the
stopPropagation( ) method.
- 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, assigned as a property of the scriptable object version
of the element, or associated with the object through event
model-specific methods (attachEvent( ) or
addEventListener( )). Each element responds to a
specific set of events.
- event propagation
The process of event information coursing its way through the element
or object hierarchy of a document. In recent browsers, an event
propagates from the window, document, or body element (depending on
the event type) inward toward the target element. At that point the
event propagation performs a U-turn, and bubbles upward through the
same container path. For an object to process an event as it passes
toward the target element, the object must be set up to capture the
event. Event bubbling is automatic for most event types.
A rendering feature of Internet Explorer 4 or later (for the Windows
platform) that adds typographic effects to text content and animated
transitions between views. 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 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. HTML is the foundation of
An identifier for an 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 every HTML 4 tag. An ID
is used for many purposes, including associating a CSS style sheet
rule with a single element among all elements of a document and
simplifying script references to a specific element.
A name assigned to an id,
class, or name attribute of an
element, as well as names for objects and variables in a scripting
language. 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
- intrinsic events
Event handlers defined by the HTML 4 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
Microsoft's name for its implementation of
A Navigator 4-only syntax for defining style sheet rules.
scripting language built into Internet Explorer 3 and later.
Derived from Navigator 4's now-abandoned model for a
positionable element, the term is currently a generic reference to
any element with a CSS position attribute assigned
a value such as absolute,
relative, or fixed. Each
positioned element exists in its own transparent layer above the main
In CSS, a region that extends outside of an
element's border. Every element
has a margin, even if its thickness is zero.
In CSS, a reference to the type of output for which the rule is to be
applied. Mainstream browsers commonly support the screen and print
media, but the other possible media include projection, audio, and
small screen displays of portable devices.
A scriptable object's action that can be initiated
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 it isn't a requirement.
- modifier key
A keyboard key that is usually pressed in concert with a character
key or mouse action 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 and mouse
events can be examined for which (if any) modifier keys were being
held down at the time of the character key's event.
A tendency in recent W3C standards tracks to divide large standards
into multiple modules, each of which has a specific focus, such as
the Events module of the W3C DOM recommendation.
In a document object model, an object that can be referenced within
the document's hierarchical structure. Some node
types act as containers of additional, nested nodes, while other
types contain nothing but document text content.
A representation of an HTML element or other programmable item in a
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 img
object, the new graphic 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.
- object detection
A scripting technique that verifies whether a browser supports a
particular object, property, or method before attempting to execute a
statement with that term in it. This technique is gaining favor over
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 visible padding to all positioned elements.
For HTML elements, the next outermost element in source code order
(the tr element that surrounds a
td element, for example). For positioned elements,
the parent element determines the coordinate plane for an
element's positioning. For scriptable window
objects, a frame's parent is the 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
XP, Mac OS X, 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-, relative-, or (in some browsers) fixed-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
because they can be scripted as properties of the
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 style sheet selector that points to a very specific piece of an
element, such as the first letter of a paragraph
- quirks (mode)
Reference to a mode whereby modern browsers emulate the nonstandard
behaviors of their earlier versions for the sake of backward
compatibility with existing HTML and CSS code. The operational mode
(quirks versus standards-compatible modes) is controlled by settings
in the <!DOCTYPE> tag for browsers such as
IE 6 and Netscape 6.
- 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 blank 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.
An acronym for red-green-blue, the three base colors (in that order)
for a popular color specification system, including those used for
HTML and CSS color-related attributes. Values for each color are in
the range between 0-255 (none to maximum saturation), in decimal or
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
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
- style sheet
In CSS, one or more rules that define 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
In Internet Explorer for Windows, a visual effect for hiding and
showing elements. Transitions are controlled via filters.
Passing source code through a program that compares the code against
a standards-based measuring stick for syntactic accuracy, structural
integrity, and adherence to standards requirements.
A scripting language alternate to JScript in Internet Explorer for
Windows. You can combine script blocks in VBScript and JScript in the
same document, and statements in each block may reference variables
and objects in the other.
An acronym for the World Wide Web Consortium (http://www.w3.org).
An acronym for the Web Accessibility Initiative activity of the W3C;
their goal is to promote web resources for users with disabilities
An acronym for the Extensible Hypertext Markup Language
recommendation of the W3C. This branch of the HTML activity is a
version of HTML implemented as an XML application (http://www.w3.org/MarkUp).
An acronym for the Extensible Markup Language recommendation of the
W3C, which provides the basis for structuring data in a way that
facilitates its storage and transfer around the Web (http://www.w3.org/XML).
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