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Appendix A: Changes

A.1 Changes between HTML 3.2 and HTML 4.0

A.1.1 Changes to elements

New elements

The new elements in HTML 4.0 are: ABBR, ACRONYM, BDO, BUTTON, COL, COLGROUP, DEL, FIELDSET, FRAME, FRAMESET, IFRAME, INS, LABEL, LEGEND, NOFRAMES, NOSCRIPT, OBJECT, OPTGROUP, PARAM, S (deprecated), SPAN, TBODY, TFOOT, THEAD, and Q.

Deprecated elements

The following elements are deprecated: APPLET, BASEFONT, CENTER, DIR, FONT, ISINDEX, MENU, STRIKE, and U.

Obsolete elements

The following elements are obsolete: LISTING, PLAINTEXT, and XMP. For all of them, authors should use the PRE element instead.

A.1.2 Changes to attributes

Almost all attributes that specify the presentation of an HTML document (e.g., colors, alignment, fonts, graphics, etc.) have been deprecated in favor of style sheets. The list of attributes in the appendix indicates which attributes have been deprecated.
The id and class attribute allow authors to assign name and class information to elements for style sheets, as anchors, for scripting, for object declarations, general purpose document processing, etc.

A.1.3 Changes for accessibility

HTML 4.0 features many changes to promote accessibility, including:

The title attribute may now be set on virtually every element.
Authors may provide long descriptions of tables (see the summary attribute), images and frames (see the longdesc attribute).

A.1.4 Changes for meta data

Authors may now specify profiles that provide explanations about meta data specified with the META or LINK elements.

A.1.5 Changes for text

New features for internationalization allow authors to specify text direction and language.
The INS and DEL elements allow authors to mark up changes in their documents.
The ABBR and ACRONYM elements allow authors to mark up abbreviations and acronyms in their documents.

A.1.6 Changes for links

The id attribute makes any element the destination anchor of a link.

A.1.7 Changes for tables

The HTML 4.0 table model has grown out of early work on HTML+ and the initial draft of HTML3.0. The earlier model has been extended in response to requests from information providers as follows:

Authors may specify tables that may be incrementally displayed as the user agent receives data.
Authors may specify tables that are more accessible to users with non-visual user agents.
Authors may specify tables with fixed headers and footers. User agents may take advantage of these when scrolling large tables or rendering tables to paged media.

The HTML 4.0 table model also satisfies requests for optional column-based defaults for alignment properties, more flexibility in specifying table frames and rules, and the ability to align on designated characters. It is expected, however, that style sheets will take over the task of rendering tables in the near future.

In addition, a major goal has been to provide backwards compatibility with the widely deployed Netscape implementation of tables. Another goal has been to simplify importing tables conforming to the SGML CALS model. The latest draft makes the align attribute compatible with the latest versions of the most popular browsers. Some clarifications have been made to the role of the dir attribute and recommended behavior when absolute and relative column widths are mixed.

A new element, COLGROUP, has been introduced to allow sets of columns to be grouped with different width and alignment properties specified by one or more COL elements. The semantics of COLGROUP have been clarified over previous drafts, and rules="basic" replaced by rules="groups".

The style attribute is included as a means for extending the properties associated with edges and interiors of groups of cells. For instance, the line style: dotted, double, thin/thick etc; the color/pattern fill for the interior; cell margins and font information. This will be the subject for a companion specification on style sheets.

The frame and rules attributes have been modified to avoid SGML name clashes with each other, and to avoid clashes with the align and valign attributes. These changes were additionally motivated by the desire to avoid future problems if this specification is extended to allow frame and rules attributes with other table elements.

A.1.8 Changes for images, objects, and image maps

The OBJECT element allows generic inclusion of objects.
The IFRAME and OBJECT elements allow authors to create embedded documents.
The alt attribute is required on the IMG and AREA elements.
The mechanism for creating image maps now allows authors to create more accessible image maps. The content model of the MAP element has changed for this reason.

A.1.9 Changes for forms

This specification introduces several new attributes and elements that affect forms:

The accesskey attribute allows authors to specify direct keyboard access to form controls.
The disabled attribute allows authors to make a form control initially insensitive.
The readonly attribute, allows authors to prohibit changes to a form control.
The LABEL element associates a label with a particular form control.
The FIELDSET element groups related fields together and, in association with the LEGEND element, can be used to name the group. Both of these new elements allow better rendering and better interactivity. Speech-based browsers can better describe the form and graphic browsers can make labels sensitive.
A new set of attributes, in combination with scripts, allow form providers to verify user-entered data.
The BUTTON element and INPUT with type set to "button" can be used in combination with scripts to create richer forms.
The OPTGROUP element allows authors to group menu options together in a SELECT, which is particularly important for form accessibility.
Additional changes for internationalization.

A.1.10 Changes for style sheets

HTML 4.0 supports a larger set of media descriptors so that authors may write device-sensitive style sheets.

A.1.11 Changes for frames

HTML 4.0 supports frame documents and inline frames.

A.1.12 Changes for scripting

Many elements now feature event attributes that may be coupled with scripts; the script is executed when the event occurs (e.g., when a document is loaded, when the mouse is clicked, etc.).

A.1.13 Changes for internationalization

HTML 4.0 integrates the recommendations of [RFC2070] for the internationalization of HTML.

However, this specification and [RFC2070] differ as follows:

The accept-charset attribute has been specified for the FORM element rather than the TEXTAREA and INPUT elements.
The HTML 4.0 specification makes additional clarifications with respect to the bidirectional algorithm.
The use of CDATA to define the SCRIPT and STYLE elements does not preserve the ability to transcode documents, as described in section 2.1 of [RFC2070].

A.2 Changes from the 18 December 1997 specification

This section describes how this version of the HTML 4.0 specification differs from the previous version released on 18 December 1997.

A.2.1 Errors that were corrected

Section 2.1.1: "http://www.w3.org/TR/PR-html4/cover.html" was said to designate the current HTML specification. The current HTML specification is actually at http://www.w3.org/TR/REC-html40.
Section 7.5.2: The hypertext link on name was incorrect. It now links to types.html#type-name.
Section 7.5.4: href was listed as an attribute of the DIV and SPAN elements. It is not.
Section 7.5.6: A P element was used in the example. It is invalid in ADDRESS.
Section 8.1: In the first example, which reads "Her super-powers were the result...", there was an extra double quote mark before the word "Her".
Section 9.3.4: The attribute width was not noted as deprecated.
Section 11.2.4, "Calculating the width of columns": The sentence "We have set the value of the align attribute in the third column group to 'center'" read "second" instead of "third".
Section 11.2.6, "Cells that span several rows or columns": The second paragraph read "In this table definition, we specify that the cell in row four, column two should span a total of three columns, including the current row." It now ends "...including the current column."
Section 13.2: The sentence beginning "User agents must render alternate text when they cannot support ..." read "next", instead of "text".
Section 13.6.2: The last sentence of the second paragraph applied to both the IMG and INPUT elements. However, the ismap attribute is not defined for INPUT. The sentence now only applies to IMG.
Section 14.2.3: The title attribute for the STYLE element was not listed as an attribute defined elsewhere.
Section 14.3.2: The second example set title="Compact". It now sets title="compact".
Section 15.1.2: The sentence ending "the align attribute." read "the align element."
Section 15.1.3.2: The CSS style rule "BR.mybr { clear: left }" was incorrect, since it refers to the class "mybr" and not the id value. The correct syntax is: "BR#mybr { clear: left }".
Section 16: All the examples containing a Document Type Declaration used something like "THE_LATEST_VERSION_/frameset.dtd" or "THE_LATEST_VERSION_" as the system identifier for the Frameset DTD. They now use "http://www.w3.org/TR/REC-html40/frameset.dtd" instead.
Section 16.3 and Section 16.3.1: The second example of 16.3 and the example of 16.3.1 used the wrong DTD; they now use the Transitional DTD.
Section 17.5: In "attributes defined elsewhere" for the BUTTON element, id, class, lang, dir, title, style, and tabindex were missing. Also, usemap has been removed.
Section 17.6/17.6.1: The "attributes defined elsewhere" for OPTION and OPTGROUP mistakenly listed onfocus, onblur, and onchange. The "attributes defined elsewhere" section was missing for the SELECT element (please see the DTD for the full list of attributes).
Section 17.9.1: The tabindex attribute was said to be defined for the LABEL element. It is not.
Section 17.12.2: The sentence "The following elements support the readonly attribute: INPUT and TEXTAREA." read "The following elements support the readonly attribute: INPUT, TEXT, PASSWORD, and TEXTAREA."
Section 18.2.2, "Local declaration of a scripting language": The first paragraph read: "It is also possible to specify the scripting language in each SCRIPT element via the type attribute. In the absence of a default scripting language specification, this attribute must be set on each SCRIPT element." Since the type attribute is required for the SCRIPT element, this paragraph now reads: "The type attribute must be specified for each SCRIPT element instance in a document. The value of the type attribute for a SCRIPT element overrides the default scripting language for that element."
Section 24.2.1 and file HTMLlat1.ent: The comment for the character reference "not" read "= discretionary hyphen". This has been removed.
The FPI in comment read "-//W3C//ENTITIES Full Latin 1//EN//HTML", instead this is now "-//W3C//ENTITIES Latin1//EN//HTML".
Section 24.3.1 and file HTMLsymbol.ent: The FPI in comment read "-//W3C//ENTITIES Symbolic//EN//HTML", instead this is now "-//W3C//ENTITIES Symbols//EN//HTML".
Section A.1.1, "New elements" (previously A.1.1) and Section A.1.1, "Deprecated elements" (previously A.1.2): The S element which is deprecated was listed as part of the changes between HTML 3.2 and HTML 4.0. This element was not actually defined in HTML 3.2. It is now in the new elements list.
Section A.1.3 (previously A.3): The longdesc attribute was said to be specified for tables. It is not. Instead, the summary attribute allows authors to give longer descriptions of tables.
Section B.4: The sentence "You may help search engines by using the LINK element with rel="start" along with the title attribute, ..." read "You may help search engines by using the LINK element with rel="begin" along with a TITLE, ..." The same stands for the companion example.
Section B.5.1: The sentence "This can be altered by setting the width attribute of the TABLE element." read "This can be altered by setting the width-TABLE attribute of the TABLE element."
Section B.5.2: The sentence "Rules for handling objects too large for a column apply when the explicit or implied alignment results in a situation where the data exceeds the assigned width of the column." read "too large for column". The meaning of the sentence was unclear since it referred to "rules" governing an error condition; user agent behavior in error conditions lies outside the scope of the specification.
Index of attributes: The href attribute for the BASE element was marked as deprecated. It is