Differences between HTML and XHTML have been noted. Differences between HTML 4.01 and HTML 5 less so. The following identifies one difference that may seem insignificant but annoys me endlessly.

[Note: The following adressess HTML 5; not XHTML 5. All HTML 4.01 text/html and XHTML 1.0 text/htmldocuments are considered to be HTML 5.1]

HTML 4.01 Specification, 7.4.4 Meta data states,

“The http-equiv attribute can be used in place of the name attribute and has a special significance when documents are retrieved via the Hypertext Transfer Protocol (HTTP). HTTP servers may use the property name specified by the http-equiv attribute to create an [RFC822]-style header in the HTTP response. Please see the HTTPspecification ([RFC2616]) for details on valid HTTP headers.”

[Note: W3C specifications do not place use limitations.]

HTML 4.01 Specification, 5.2.2 Specifying the character encoding states,

“META declarations should appear as early as possible in the HEAD element.”


Web Applications 1.0 allows one (1) http-equiv: character set. And, it must be placed first in the <head> section.

Web Applications 1.0, 3. Semantics and structure of HTML elements, 3.8. Document metadata, 3.8.5. The meta element offers,

Metadata element
Contexts in which this element may be used:
In a head element.
Content model:
Element-specific attributes:
http-equiv (HTML only, optional [Elementary emphasis.])
Predefined classes that apply to this element:
DOM interface:
interface HTMLMetaElement : HTMLElement {
attribute DOMString content;
attribute DOMString name;