"One smell of the day" the difference between HTML and XHTML-------HTML and XHTML

Extensible Hypertext Markup Language XHTML (extensible Hypertext Markup Language), the first revision of HTML 4.01, is the "3 HTML4 files reorganized according to the XML1.0 standard". In other words, XHTML is a hybrid of HTML 4.01 and XML1.0.
Since XHTML1.0 is based on HTML4.01 and does not introduce any new tags or attributes (xhtml can be thought of as a subset of HTML), it behaves like Hypertext Markup Language HTML, but is syntactically stricter, and almost all Web browsers, while parsing HTML correctly, can be XHTML compatible.
For example: All tags in xhtml must be lowercase, all tags must be closed, and each attribute must be enclosed in quotation marks. <br> to be written <br/>, cannot be written as <br/> (with HR); After using <p>, you must have a </p> to end the paragraph.

"One smell of the day" the difference between HTML and XHTML-------HTML and XHTML