HTML
, which stands for Hyper Text Markup Language, is a descriptive language. XHTML
, which stands for Extensible HyperText Markup Language, is also a descriptive language, similar to HTML
in terms of presentation, but with stricter syntax. In terms of relationship, HTML
is an application based on the Standard Generalized Markup Language (SGML
), XML
is a subset of SGML
, and XHTML
is based on XML
.
XHTML
is based on the Extensible Markup Language (XML
).HTML
is based on the Standard Generalized Markup Language (SGML
).HTML
has looser syntax requirements.XHTML
requires elements to be closed, including empty tags.XHTML
tag names must be in lowercase.XHTML
documents must have a root element.XHTML
tag order must be correct.XHTML
documents require all attributes to have a value, and attribute values cannot be abbreviated.XHTML
requires all attributes to be enclosed in double quotation marks (""
).XHTML
documents need to encode special characters such as <
, >
, &
, etc.XHTML
documents cannot use --
in comment content.XHTML
images must have alt text.XHTML
documents use the id
attribute instead of the name
attribute.XHTML
can incorporate various XML
applications, such as MathML
and SVG
.HTML4.0
cannot incorporate other XML
applications, but in HTML5
, it is possible to embed applications such as MathML
and SVG
.