XHTML

XHTML (Extensible Hypertext Markup Language) is a markup language that is used to create and display web pages. It was first introduced in 2000 and is a stricter and cleaner version of HTML (Hypertext Markup Language). XHTML follows the rules and syntax of XML (Extensible Markup Language), which means that it is more structured and more easily parseable than HTML. XHTML is designed to be compatible with existing HTML browsers while also being more easily parsed by computer programs.

Purpose and Usage

The purpose of XHTML is to provide a more structured and standardized way of creating web pages. It is designed to be more easily parsed by computer programs, which makes it easier to create complex web applications. XHTML is also designed to be compatible with existing HTML browsers, which means that it can be used on any device that can display web pages.

XHTML is used to create web pages that are more accessible to people with disabilities. It provides a way to mark up content in a way that can be easily interpreted by screen readers and other assistive technologies. This is achieved by using semantic markup to describe the content of a web page. For example, headings are marked up using the <h1> to <h6> tags, which makes it easier for a screen reader to navigate the page.

XHTML is also used to create mobile-friendly web pages. XHTML allows web developers to create web pages that are optimized for mobile devices by using responsive design techniques. This means that the web page can adapt to different screen sizes and resolutions, making it easier to view on a mobile device.

Syntax

XHTML follows the same basic syntax as HTML. It consists of a series of tags that are used to mark up content. Tags are enclosed in angle brackets < > and are usually paired with a closing tag. For example, the <p> tag is used to mark up a paragraph of text:

<p>This is a paragraph of text.</p>

In XHTML, all tags must be closed properly. This means that every opening tag must have a corresponding closing tag. For example, the following code is invalid in XHTML:

<p>This is a paragraph of text.

To be valid XHTML, it should be written like this:

<p>This is a paragraph of text.</p>

XHTML also requires that all tags be lowercased. For example, the <P> tag in HTML should be written as <p> in XHTML.

XHTML also requires that all attributes be enclosed in quotes. For example, the class attribute should be enclosed in quotes like this:

<div class="container">...</div>

Differences from HTML

XHTML is stricter than HTML in its syntax and rules. The following are some of the main differences between XHTML and HTML:

Case Sensitivity

XHTML is case sensitive, which means that all tags and attribute names must be lowercase. In HTML, tags and attribute names can be uppercase or lowercase.

Closing Tags

XHTML requires that all tags be closed properly. This means that every opening tag must have a corresponding closing tag. In HTML, some tags can be left unclosed.

Attribute Quotes

XHTML requires that all attributes be enclosed in quotes. In HTML, attribute quotes are optional.

XML Conformance

XHTML follows the syntax and rules of XML, which means that it is more structured and more easily parsed than HTML. XHTML also requires that all tags be nested properly and that all attributes be defined.

Advantages of Using XHTML

There are several advantages to using XHTML over HTML:

Structural Integrity

XHTML has a more structured syntax than HTML, which means that it is less prone to errors. This makes it easier to create complex web pages and applications.

Compatibility

XHTML is designed to be compatible with existing HTML browsers, which means that it can be used on any device that can display web pages.

Accessibility

XHTML provides a way to create web pages that are more accessible to people with disabilities. By using semantic markup, web developers can make it easier for screen readers and other assistive technologies to interpret the content of a web page.

Mobile Optimization

XHTML allows web developers to create web pages that are optimized for mobile devices. By using responsive design techniques, web developers can ensure that web pages are easy to view on a variety of screen sizes and resolutions.