Difference between HTML and XHTML?

[hp-singh-53e2639c (Harjas Preet Singh)]

Difference between HTML and XHTML?

[anik-acharjee]

1. HTML stands for Hypertext Markup Language whereas XHTML stands for Extensible Hypertext Markup Language.
2. HTML is extended from SGML whereas XHTML is extended from XML and HTML.
3. In HTML, all tags and attributes are not necessarily to be in lower or upper case whereas in XHTML, every tag and attribute should be in lower case.
4. Doctype is not necessary to write at the top in HTML whereas Doctype is very necessary to write at the top of the file in XHTML.
5. In HTML, filename extension used are .html, .htm. whereas in XHTML, filename extension are .xhtml, .xht, .xml.