XHTML Standards
Understanding the evolution of HTML into the strictly validated XHTML.
XHTML stands for Extensible HyperText Markup Language. It represents a much stricter, XML-based evolution of standard HTML.
Why do we care about XHTML?
While modern HTML5 is incredibly forgiving with loose syntax (missing closing tags, unquoted attributes), XHTML forces developers to write perfectly clean and well-formed code. This strictness ensures that lightweight devices, custom parsers, and specialized screen readers can accurately interpret the web content without guessing what the developer meant.
The Golden Rules of XHTML
If you plan to write code that adheres to XHTML standards, you must conform to a few structural laws:
- Rule 1: The
<!DOCTYPE>declaration is mandatory. - Rule 2: All elements must be accurately nested without overlap.
- Rule 3: Every single tag must be closed (even empty ones like
<br />). - Rule 4: Tag names and attributes must be written entirely in lowercase.
- Rule 5: Attribute values must instantly be wrapped in quotation marks.
Closing the Loop
By writing your regular HTML5 code with the strictness and discipline of XHTML, you naturally produce higher quality, incredibly robust applications that are significantly less prone to quirky cross-browser bugs.