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Dynamic Web Page - what is it?

A Web page that is returned to the user with custom content based on the results of a search or some other request. Also known as "dynamic HTML" or "dynamic content," the "dynamic" word is used with Web sites to refer to custom results individualized to each user in contrast to the billions of static Web pages that do not change.

For decades, query and report programs have delivered custom content to the user based on a request. Although one might have said the results were "dynamically created" by the application, the "dynamic" word was not typically applied to the content itself like it is today regarding the Web.

The term "dynamic Web page" is sometimes used to refer to pages which contain moving images or scrolling text. Such pages may simply use dynamic GIFs, may use multimedia formats such as Macromedia's Flash technology or may make use of a language such as ECMAscript (JavaScript) or Java.
The term "dynamic Web site" may also refer to Web sites which provide interfaces to search facilities or backend databases, in which server-side technologies (such as CGI) are used to interrogate databases, file store or legacy systems held on the server and display results based on a user query; for example a Web site which provides access to a library OPAC.
The term "dynamic Web page" may also be used to refer to pages which may be personalised for the end user, either by the end user selecting preferred options or by the system choosing the preferred options based on the end user profile. An example is the My.Netscape service (which allows users to select the resources which are displayed, from options such as weather information, news, horoscopes, etc.).
The term "dynamic Web page" may also be refer to pages which are personalised for the end user's device or browser. For example, different pages may be sent to Netscape and Internet Explorer browsers, to users of browsers for the visually impaired, WebTVs, PDAs or WAP phones.
The term "dynamic Web page" may also be refer to pages which will alter based on actions by the end user. For example a menu may expand as the user moves the cursor over the menu item. This approach is normally provided by use of a client-side scripting language such as ECMAscript (JavaScript) which will manipulate HTML and CSS elements based on end user actions, such as mouse movements and mouse clicks. The term "Dynamic HTML" (DHTML) is often used in this context.
The term "dynamic Web site" may be used to refer to a Web site which makes use of a server-side scripting environment such as PHP or ASP (Active Server Pages) or a content management system such as Zope or ColdFusion. It should be noted that such technologies may be used to provide dynamic Web pages (as defined in 1-5) but they may also be used to provide static Web pages.

Dynamic HTML is a collective term for a combination of new Hypertext Markup Language (HTML) tags and options, that will let you create Web pages more animated and more responsive to user interaction than previous versions of HTML. Much of dynamic HTML is specified in HTML 4.0. Simple examples of dynamic HTML pages would include (1) having the color of a text heading change when a user passes a mouse over it or (2) allowing a user to "drag and drop" an image to another place on a Web page. Dynamic HTML can allow Web documents to look and act like desktop applications or multimedia productions.

The features that constitute dynamic HTML are included in Netscape Communications' latest Web browser, Navigator 4.0 (part of Netscape's Communicator suite), and by Microsoft's browser, Internet Explorer 4.0. While HTML 4.0 is supported by both Netscape and Microsoft browsers, some additional capabilities are supported by only one of the browsers. The biggest obstacle to the use of dynamic HTML is that, since many users are still using older browsers, a Web site must create two versions of each site and serve the pages appropriate to each user's browser version.

The Concepts and Features in Dynamic HTML

Both Netscape and Microsoft support:

An object-oriented view of a Web page and its elements
Cascading style sheets and the layering of content
Programming that can address all or most page elements
Dynamic fonts

An Object-Oriented View of Page Elements

Each page element (division or section, heading, paragraph, image, list, and so forth) is viewed as an "object." (Microsoft calls this the "Dynamic HTML Object Model." Netscape calls it the "HTML Object Model." W3C calls it the "Document Object Model.") For example, each heading on a page can be named, given attributes of text style and color, and addressed by name in a small progam or "script" included on the page. This heading or any other element on the page can be changed as the result of a specified event such a mouse passing over or being clicked or a time elapsing. Or an image can be moved from one place to another by "dragging and dropping" the image object with the mouse. (These event possibilities can be viewed as the reaction capabilities of the element or object.) Any change takes place immediately (since all variations of all elements or objects have been sent as part of the same page from the Web server that sent the page). Thus, variations can be thought of as different properties of the object.

Not only can element variations change text wording or color, but everything contained within a heading object can be replaced with new content that includes different or additional HTML as well as different text. Microsoft calls this the "Text Range technology."

Style Sheets and Layering

A describes the default style characteristics (including the page layout and font type style and size for text elements such as headings and body text) of a document or a portion of a document. For Web pages, a style sheet also describes the default background color or image, hypertext link colors, and possibly the content of page. Style sheets help ensure consistency across all or a group of pages in a document or a Web site.

Dynamic HTML includes the capability to specify style sheets in a "cascading style sheet" fashion (that is, linking to or specifying different style sheets or style statements with predefined levels of precedence within the same or a set of related pages). As the result of user interaction, a new style sheet can be made applicable and result in a change of appearance of the Web page. You can have multiple layers of style sheet within a page, a style sheet within a style sheet within a style sheet. A new style sheet may only vary one element from the style sheet above it. Layering is the use of alternate style sheets or other approaches to vary the content of a page by providing content layers that can overlay (and replace or superimpose on) existing content sections. Layers can be programmed to appear as part of a timed presentation or as the result of user interaction. In Internet Explorer 4.0, Microsoft implements layers through style sheets. Netscape supports the style sheet approach but also offers a new HTML ...tag set (that Microsoft does not support). Both approaches are being considered by the W3C Working Committee and both companies say they will support whatever W3C decides will be the recommended approach.

Programming

Although JavaScript, Java applet, and ActiveX controls were present in previous levels of Web pages, dynamic HTML implies an increased amount of programming in Web pages since more elements of a page can be addressed by a program.

Dynamic Fonts

Netscape includes dynamic fonts as part of dynamic HTML. This feature of Netscape's Navigator browser in its Communicator suite lets Web page designers include font files containing specific font styles, sizes, and colors as part of a Web page and to have the fonts downloaded with the page. That is, the font choice no longer is dependent on what the browser provides.