XHTML 1.0 and HTML 4.0, the precursors to HTML5 consist of the same sets of elements. HTML5, the latest version of HTML, introduces some new elements that will be covered in this course. The only difference between HTML and XHTML is that HTML is fairly flexible, whereas XHTML has strict rules.
HTML has a long history and several versions. Therefore, web pages exist that use deprecated tags and outdated techniques, such as formatting
<i> tags to bold or italicize text.
But with the introduction of HTML5, there is an easy way out, which we highly recommend as it is both simpler and forward compatible.
Older versions of HTML had complicated DOCTYPEs, but these days you can simply use the new HTML5 DOCTYPE:
This DOCTYPE is completely backward compatible and will make all browsers work in "standards mode."