Although XHTML is dead, many of these rules have never been questioned again. If a user agent encounters an attribute it does not recognize, it must ignore the entire attribute specification (i.e., the attribute and its value). XHTML documents must use lower case for all HTML element and attribute names. Please refer to the errata for this document, which may include some normative corrections. Instead of using name = "name", XHTML prefers to use id = "id". Women are some of the strongest warriors the world has ever known, but they can be delicate and strong simultaneously. Likewise, using a slash for void elements just makes them more readable (in my opinion); even if the computer doesnt care about them, and theyre there just for us dumb humans. These are handled inconsistently by user agents. For non-empty elements, end tags are not always required. Element and attribute names may be lower or upper case. And while the use of extension elements isnt as bad as before HTML4/5 standards, it still has to be accounted for. There were reasons everyone preferred XHTML back in the early 00s. must specify the xml namespace for the document. In the 1990s, there was HTML. Use both the lang and xml:lang attributes when specifying the language of an element. Every time you have special rules, you have to explain those to new team members, and they will get them wrong. The html, head, title, and body elements must be present. Otherwise, your XHTML document is assumed as an invalid document. For compatibility with these types of legacy browsers, you may want to avoid using processing instructions and XML declarations. Those HTML files looked terrible and deserved to die. In the example, Href and anchor tag A are not in lower case, so it is incorrect. Here is the example showing syntax , XHTML does not allow attribute minimization. What Is Attribute Minimization In Html merry Answer: The use of checked in this way is referred to as attribute minimization. Must not contain the ,