Technology Comparison

Microsoft Corporation

Updated: September 30, 1997

Microsoft Dynamic HTML and Netscape Dynamic HTML

How do Microsoft's and Netscape's implementations of Dynamic HTML compare? Both technologies support Cascading Style Sheets, specifically the CSS Recommendation and CSS Positioning Working Draft . Apart from CSS support, these two technologies fundamentally differ with respect to creative capabilities and standards support.

Microsoft Dynamic HTML provides Web authors with a powerful HTML layout engine and total creative control, so they can manipulate any page element at any time.

Netscape's implementation is not consistent with the Document Object Model, as described by the W3C Requirements Document. As a result, Netscape Navigator exposes few page elements as objects, limiting layout and creative capabilities for authors. Page elements can be manipulated only while the page is loading, not after load time. Netscape's nonstandard implementation consists of JavaScript Accessible Style Sheets (JASS), layers and dynamic fonts (TrueDoc). These technologies are not supported in Microsoft Internet Explorer 4.0.

JASS lets content providers specify document style only while the page is loading, not after load time. The Document Object Model, supported by Microsoft Dynamic HTML, provides Web authors greater flexibility and power by enabling them to change page content at any time. The Document Object Model also better meets author needs in that it is language-neutral, unlike JASS, which is JavaScript-dependent.
Layers technology consists of the proprietary <LAYER> and <ILAYER> tags. Given that these tags are not consistent with the long-term direction of HTML, which is to separate page content from presentation, Netscape's layers proposal has been rejected by the W3C. Both Microsoft Internet Explorer 4.0 and Netscape Navigator 4.0 support CSS positioning, a standard and cross-browser way to position page elements.
Netscape's dynamic fonts use proprietary TrueDoc technology and proprietary HTML extensions. Microsoft Internet Explorer 4.0 partially supports the W3C Web Fonts Working Draft .

Microsoft's implementation of Dynamic HTML, based on the Document Object Model, provides greater creative control than Netscape's implementation, which provides little support for the Document Object Model.

For instance, with Netscape's implementation of Dynamic HTML, an author could replace one graphic with another on a Web page. Because Netscape's technology does not include intelligence about the relationships among page elements, the text surrounding the replaced graphic would not reflow. For the same reason, authors cannot dynamically change the font size of selected text. An interactive document, such as a table of contents or an outline, could not be created using Netscape technology without reloading the page.

In-Depth Comparison

Total Creative Control for Rich User Experience

Microsoft Dynamic HTML Netscape Dynamic HTML

Comprehensive object model

Supports Document Object Model. All page elements (every element, attribute, and even characters in a document) are programmable objects.
All elements can generate events. Mouse and keyboard events are surfaced for all elements.
Events bubble through the document hierarchy.
Page contents are accessible to scripts.
Limited object model

Provides little support for Document Object Model. Few elements are encapsulated as objects, so little page content can be manipulated by script.
Very few elements can generate events.
No event bubbling.

Interactive content

Access and manipulate (create, delete, or modify) all existing document content at any time.
Readjust all page elements automatically around new content.
None

Dynamic styles

After load time, change the style (e.g., font, color) of existing content.
Apply filter and transition effects to HTML through CSS syntax.
None

Positioning, limited animation

Supports CSS positioning.
Animate elements by changing CSS position attributes at any time.
Create 2-D forms, where each form element is absolutely positioned.
Support for scrolling content when an element's content exceeds its height or width.
Access any existing page content. Move this content anywhere at any time, without having to redefine the content.
The relationship among page elements is known. If an element changes, then other page elements readjust automatically without the page having to reload (e.g., An element can be resized, and other page content will reflow around that element).
Positioning, limited animation

Supports CSS positioning.
Multiple, static layers must be used to simulate animation of page elements.
Form elements cannot be absolutely positioned in a 2-D form.
Content does not scroll when its height or width has been exceeded.
Authors have very limited access to, and thus cannot manipulate, existing page content.
The relationship among page elements is not known. Page elements do not readjust automatically, unless the entire page is reloaded (e.g., page elements must maintain a fixed size).

Load time interactivity

Update document's style or content while page is parsed.
Display page in canvas mode.
Limited load time interactivity

JASS style attributes are updated at load time.
Display page in canvas mode.

Data binding

Ability to cache and present data locally.
Manipulate (e.g., sort, filter) data without a server round trip.
Supports different data sources: ODBC, JDBC, comma-delimited text files through data source objects that retrieve and provide data to Web page.
Supports JavaBeans, ActiveX™ interfaces. Data source objects can be Java applets or ActiveX controls.
None

Scriptlets

Create components using HTML and script (EMCAScript, VBScript).
Easily customize, reuse these components through well-defined interfaces.
None

Easiest Way to Make Pages Interactive

Simple scripting

One model for using Dynamic HTML.
Reuse code with event bubbling.
Scripting more complex

Need to learn how to use two different models: JASS and layers. Layers can require complex scripting.
No event bubbling.

Language independent

Supports any language (e.g., JavaScript, VBScript). Extend with ActiveX Controls, Java applets.
JavaScript only

Third-party tools support

Tools available today from : Bluestone, ExperTelligence, Microsoft, Pictorius, SoftQuad
Tools coming soon from Allaire, Borland, Elemental, Macromedia, Powersoft
No support announced

Open Technology

Open object model

Independent of language or object technology.
Based on W3C Document Object Model preliminary requirements.
Limited object model

Tied to JavaScript.
Provides little Document Object Model functionality.

Graceful degradation

CSS, HTML 3.2 content displayed statically in other browsers.
Less graceful degradation

CSS, HTML 3.2 content displayed statically in other browsers.
Layers not displayed well in other browsers.

Availability

Microsoft Internet Explorer 4.0 on the Macintosh, Windows®, and UNIX platforms.
Dynamic HTML to be licensed freely to third parties.
Limited availability

Netscape Communicator for Macintosh, Windows, and UNIX platforms.
Dynamic HTML implementation not available to third parties.

Support for Standards

Internet Explorer Navigator 4.0

Recommendations

HTML 3.2
CSS1
PNG

Yes
Yes
Yes

Yes
Yes
No(1)

Working Drafts

Positioning HTML elements with CSS
Web fonts

Yes

Partial

Yes

No(2)

HTML 4.0:

- Hypertext links in HTML Yes Yes

- HTML and style sheets Yes Yes

- Client-side scripting and HTML Yes Yes

- Implementing HTML frames Yes Partial(3)

- Enhancing interactive HTML documents (forms) Yes No

- Inserting objects into HTML Yes N/A(4)

- Additional named entities for HTML Yes No

- XML Partial(5) No

- RFC 1867: file upload requests Yes(2) Yes

- RFC 1942: HTML tables (enhancements) Yes No

- RFC 2070: HTML internationalization Yes Partial

Proposals Under Review

Document Object Model
HTML Extensions for Data Binding
XML Web Collections

Yes
Yes
No

No
No
No

Total Creative Control for Rich User Experience
Microsoft Dynamic HTML	Netscape Dynamic HTML
Comprehensive object model Supports Document Object Model. All page elements (every element, attribute, and even characters in a document) are programmable objects. All elements can generate events. Mouse and keyboard events are surfaced for all elements. Events bubble through the document hierarchy. Page contents are accessible to scripts.	Limited object model Provides little support for Document Object Model. Few elements are encapsulated as objects, so little page content can be manipulated by script. Very few elements can generate events. No event bubbling.
Interactive content Access and manipulate (create, delete, or modify) all existing document content at any time. Readjust all page elements automatically around new content.	None
Dynamic styles After load time, change the style (e.g., font, color) of existing content. Apply filter and transition effects to HTML through CSS syntax.	None
Positioning, limited animation Supports CSS positioning. Animate elements by changing CSS position attributes at any time. Create 2-D forms, where each form element is absolutely positioned. Support for scrolling content when an element's content exceeds its height or width. Access any existing page content. Move this content anywhere at any time, without having to redefine the content. The relationship among page elements is known. If an element changes, then other page elements readjust automatically without the page having to reload (e.g., An element can be resized, and other page content will reflow around that element).	Positioning, limited animation Supports CSS positioning. Multiple, static layers must be used to simulate animation of page elements. Form elements cannot be absolutely positioned in a 2-D form. Content does not scroll when its height or width has been exceeded. Authors have very limited access to, and thus cannot manipulate, existing page content. The relationship among page elements is not known. Page elements do not readjust automatically, unless the entire page is reloaded (e.g., page elements must maintain a fixed size).
Load time interactivity Update document's style or content while page is parsed. Display page in canvas mode.	Limited load time interactivity JASS style attributes are updated at load time. Display page in canvas mode.
Data binding Ability to cache and present data locally. Manipulate (e.g., sort, filter) data without a server round trip. Supports different data sources: ODBC, JDBC, comma-delimited text files through data source objects that retrieve and provide data to Web page. Supports JavaBeans, ActiveX™ interfaces. Data source objects can be Java applets or ActiveX controls.	None
Scriptlets Create components using HTML and script (EMCAScript, VBScript). Easily customize, reuse these components through well-defined interfaces.	None
Easiest Way to Make Pages Interactive
Simple scripting One model for using Dynamic HTML. Reuse code with event bubbling.	Scripting more complex Need to learn how to use two different models: JASS and layers. Layers can require complex scripting. No event bubbling.
Language independent Supports any language (e.g., JavaScript, VBScript). Extend with ActiveX Controls, Java applets.	JavaScript only
Third-party tools support Tools available today from : Bluestone, ExperTelligence, Microsoft, Pictorius, SoftQuad Tools coming soon from Allaire, Borland, Elemental, Macromedia, Powersoft	No support announced
Open Technology
Open object model Independent of language or object technology. Based on W3C Document Object Model preliminary requirements.	Limited object model Tied to JavaScript. Provides little Document Object Model functionality.
Graceful degradation CSS, HTML 3.2 content displayed statically in other browsers.	Less graceful degradation CSS, HTML 3.2 content displayed statically in other browsers. Layers not displayed well in other browsers.
Availability Microsoft Internet Explorer 4.0 on the Macintosh, Windows®, and UNIX platforms. Dynamic HTML to be licensed freely to third parties.	Limited availability Netscape Communicator for Macintosh, Windows, and UNIX platforms. Dynamic HTML implementation not available to third parties.
Support for Standards
	Internet Explorer	Navigator 4.0
Recommendations HTML 3.2 CSS1 PNG	Yes Yes Yes	Yes Yes No(1)
Working Drafts Positioning HTML elements with CSS Web fonts	Yes Partial	Yes No(2)
HTML 4.0:
- Hypertext links in HTML	Yes	Yes
- HTML and style sheets	Yes	Yes
- Client-side scripting and HTML	Yes	Yes
- Implementing HTML frames	Yes	Partial(3)
- Enhancing interactive HTML documents (forms)	Yes	No
- Inserting objects into HTML	Yes	N/A(4)
- Additional named entities for HTML	Yes	No
- XML	Partial(5)	No
- RFC 1867: file upload requests	Yes(2)	Yes
- RFC 1942: HTML tables (enhancements)	Yes	No
- RFC 2070: HTML internationalization	Yes	Partial
Proposals Under Review Document Object Model HTML Extensions for Data Binding XML Web Collections	Yes Yes No	No No No

Notes:

PNG support requires third-party plug-in.
Supports a non-standard syntax for font embedding
No <IFRAME> support.
Information not available.
Microsoft Internet Explorer 4.0 supports a few XML applications, such as CDF, but not XML generally. A future version of Internet Explorer will support XML.