HTML (HyperText Markup Language) is the standard language used to create and design the structure of web pages. It provides the basic framework, including headings, paragraphs, links, images, and other elements.

HTML is more forgiving with syntax errors, while XHTML is a stricter version of HTML based on XML. XHTML requires all tags to be properly closed, attributes to be quoted, and elements to be properly nested.

Semantic elements clearly define their meaning in the context of a web page, such as <header>, <footer>, <article>, and <section>. They improve accessibility and SEO.

Inline elements occupy only as much width as necessary and do not start on a new line (e.g., <span>). Block elements occupy the entire width and start on a new line (e.g., <div>). Inline-block elements behave like inline elements but allow height and width adjustments.

The <DOCTYPE> declaration specifies the HTML version and ensures that the browser renders the page correctly by adhering to web standards.

HTML supports three types of lists:

• Ordered List (<ol>)
• Unordered List (<ul>)
• Definition List (<dl>)

The <link> tag defines a link to external resources such as stylesheets. The <a> tag is used to create hyperlinks for navigation.

The <meta> tag provides metadata about the HTML document, such as character encoding, viewport settings, and page description for search engines.

JavaScript can be included using the <script> tag, either inline within the HTML file or as an external script by linking to a .js file.

The <div> tag is a block-level element used to group other elements, whereas the <span> tag is an inline element used to style or manipulate text within a line.