Editing HTML (section)

=== Transitional versus strict ===
HTML 4 defined three different versions of the language: Strict, Transitional (once called Loose), and Frameset. The Strict version is intended for new documents and is considered best practice, while the Transitional and Frameset versions were developed to make it easier to transition documents that conformed to older HTML specifications or did not conform to any specification to a version of HTML 4. The Transitional and Frameset versions allow for presentational markup, which is omitted in the Strict version. Instead, [[cascading style sheets]] are encouraged to improve the presentation of HTML documents. Because XHTML 1 only defines an XML syntax for the language defined by HTML 4, the same differences apply to XHTML 1 as well.

The Transitional version allows the following parts of the vocabulary, which are not included in the Strict version:
* '''A looser content model'''
** Inline elements and plain text are allowed directly in: <code>body</code>, <code>blockquote</code>, <code>form</code>, <code>noscript</code> and <code>noframes</code>
* '''Presentation related elements'''
** underline (<code>u</code>) (Deprecated. can confuse a visitor with a hyperlink.)
** strike-through (<code>s</code>)
** <code>center</code> (Deprecated. use CSS instead.)
** <code>font</code> (Deprecated. use CSS instead.)
** <code>basefont</code> (Deprecated. use CSS instead.)
* '''Presentation related attributes'''
** <code>background</code> (Deprecated. use CSS instead.) and <code>bgcolor</code> (Deprecated. use CSS instead.) attributes for <code>body</code> (required element according to the W3C.) element.
** <code>align</code> (Deprecated. use CSS instead.) attribute on <code>div</code>, <code>form</code>, paragraph (<code>p</code>) and heading (<code>h1</code>...<code>h6</code>) elements
** <code>align</code> (Deprecated. use CSS instead.), <code>noshade</code> (Deprecated. use CSS instead.), <code>size</code> (Deprecated. use CSS instead.) and <code>width</code> (Deprecated. use CSS instead.) attributes on <code>hr</code> element
** <code>align</code> (Deprecated. use CSS instead.), <code>border</code>, <code>vspace</code> and <code>hspace</code> attributes on <code>img</code> and <code>object</code> (caution: the <code>object</code> element is only supported in Internet Explorer (from the major browsers)) elements
** <code>align</code> (Deprecated. use CSS instead.) attribute on <code>legend</code> and <code>caption</code> elements
** <code>align</code> (Deprecated. use CSS instead.) and <code>bgcolor</code> (Deprecated. use CSS instead.) on <code>table</code> element
** <code>nowrap</code> (Obsolete), <code>bgcolor</code> (Deprecated. use CSS instead.), <code>width</code>, <code>height</code> on <code>td</code> and <code>th</code> elements
** <code>bgcolor</code> (Deprecated. use CSS instead.) attribute on <code>tr</code> element
** <code>clear</code> (Obsolete) attribute on <code>br</code> element
** <code>compact</code> attribute on <code>dl</code>, <code>dir</code> and <code>menu</code> elements
** <code>type</code> (Deprecated. use CSS instead.), <code>compact</code> (Deprecated. use CSS instead.) and <code>start</code> (Deprecated. use CSS instead.) attributes on <code>ol</code> and <code>ul</code> elements
** <code>type</code> and <code>value</code> attributes on <code>li</code> element
** <code>width</code> attribute on <code>pre</code> element
* '''Additional elements in Transitional specification'''
** <code>menu</code> (Deprecated. use CSS instead.) list (no substitute, though the unordered list, is recommended)
** <code>dir</code> (Deprecated. use CSS instead.) list (no substitute, though the unordered list is recommended)
** <code>isindex</code> (Deprecated.) (element requires server-side support and is typically added to documents server-side, <code>form</code> and <code>input</code> elements can be used as a substitute)
** <code>applet</code> (Deprecated. use the <code>object</code> element instead.)
* '''The <code>language</code> (Obsolete) attribute on script element''' (redundant with the <code>type</code> attribute).
* '''Frame related entities'''
** <code>iframe</code>
** <code>noframes</code>
** <code>target</code> (Deprecated in the <code>map</code>, <code>link</code> and <code>form</code> elements.) attribute on <code>a</code>, client-side image-map (<code>map</code>), <code>link</code>, <code>form</code> and <code>base</code> elements

The Frameset version includes everything in the Transitional version, as well as the <code>frameset</code> element (used instead of <code>body</code>) and the <code>frame</code> element.