3 AnswersNew Answer
Some differences between HTML5 and XHTML: XHTML is hybrid between HTML and XML, whereas HTML5 is a version of HTML. XHTML and HTML are two different ways of representing markup.XHTML is almost identical to HTML 4.01. HTML5 is the latest version of HTML.In XHTML, all tags, once opened, must be closed. HTML is less strict.XHTML has some restrictions about what tags can be nested inside each other. XHTML is stricter version of HTML; HTML5 is an upgrade of HTML.XHTML uses XML parsing requirements. HTML uses its own.HTML does not have a well-formedness constraint, no errors are fatal. In XHTML, well-formedness errors are fatal.In HTML5, one does not need to manually declare the namespace.In HTML5, one does not need to add type attributes to script and style elements.In HTML5, one must use <!DOCTYPE html>, instead of a long doctype.In HTML5, the charset declaration is much simpler.In HTML5, one does not have a choice to include or not include a dtd uri in the doctype or a choice between transitional and strict.In HTML5, one can use embed if needed.XHTML 5 is the XML serialization of HTML 5.“[HTML 5] is intended to replace XHTML 1.0 as the normative definition of the XML serialization of the HTML vocabulary."
learn html and then html 5 then the other like css and jquery and go on more on web like sql and asp.net
some syntax and versions i think