HTML (HyperText Markup Language) and XHTML (eXtensible HyperText Markup Language) are both markup languages used for creating web pages, but they have some key differences:
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Syntax Strictness:
- HTML: More lenient, allowing for some flexible markup practices, such as unclosed tags or attributes without quotes.
- XHTML: Requires stricter XML formatting, with all tags properly closed, attribute values enclosed in quotes, and elements correctly nested.
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Document Structure:
- HTML: The DOCTYPE is typically defined as
<!DOCTYPE html>, and it is case-insensitive. - XHTML: As an XML application, it must be defined as
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">, and it is case-sensitive for elements and attributes (usually using lowercase).
- HTML: The DOCTYPE is typically defined as
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Error Handling:
- HTML: Browsers typically correct erroneous HTML code, allowing it to display correctly.
- XHTML: Due to its XML nature, errors often cause the page to display incorrectly or fail to render.
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Compatibility and Application:
- HTML: Almost all browsers support HTML, including older ones.
- XHTML: While most modern browsers support XHTML, compatibility issues may arise in older browsers.
Example Illustration:
Assume you have a paragraph element to display on the page.
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In HTML, you can write:
html<p>This is a paragraphAlthough the
<p>tag is not closed, most browsers still display it correctly. -
In XHTML, you must write:
xml<p>This is a paragraph</p>Each tag must be properly closed; otherwise, the page may not render.
Overall, the introduction of XHTML was primarily to enhance web page usability and compatibility by introducing stricter standards to ensure consistency across different devices and browsers. However, with the promotion of HTML5, HTML has gradually adopted many of XHTML's strict features, reducing the differences between the two.