Changes between HTML 3.2 and HTML 4.0

Changes to elements 

New elements 

Q,

Q is intended for short quotations that don't require paragraph breaks. Here is a BLOCKQUOTE with the new cite attribute:

A good site isn't built only by brilliant programmers, or by talented graphic artists, or by lucid content authors, or by insightful managers. It will be built by their synergy, each one respecting the contributions of the others, and feeding off it for the inspiration for their own creativity. Building the web is a collaboration at all levels.

INS, DEL,

INS is used to markup sections of the document that have been inserted since a previous version of a document. DEL is used to markup sections of the document that have been deleted since a previous version of a document.

ACRONYM,

The ACRONYM element allows authors to clearly indicate a sequence of characters that compose an acronym such as WDVL. This is useful to spell checkers, speech synthesizers, and other user agents and tools. The content of the ACRONYM element specifies the acronym itself, while the title attribute may be used to provide the expanded text.

Deprecated elements 

The following elements are scheduled to become obsolete:

ISINDEX,

ISINDEX was a primitive forms-precursor. Although essentially simpler, it required a program to generate it (you couldn't just place the tag in a static HTML document since the URL it came from was used to determine the processing agent) and was extremely limited. There is no application of ISINDEX that cannot be done better with FORMS.

APPLET,

Use OBJECT instead.

CENTER,

Use DIV or style sheets instead.

FONT,

Use style sheets instead.

BASEFONT,

Use style sheets instead.

STRIKE, S,

HTML 4.0 introduces INS and DEL to show added and removed material. For a strikethrough effect for presentation purposes, use style sheets instead of S or STRIKE.

U,

U is a confusing physical style (many people see underlined text and believe it to be a link).

DIR, and MENU.

Since they are treated as identical to UL by most browsers, use UL instead of DIR or MENU.

Obsolete elements 

The following elements are now obsolete: XMP, PLAINTEXT, and LISTING. For all of them, you should use the PRE element instead. Note that PRE is not a full replacement for XMP; you need to replace <'s with &lt;'s and >'s with &gt;'s.