Opening and Closing Tags

Opening Tag

An opening tag indicates the start of an HTML element. It consists of the element name enclosed within angle brackets (< and >), (less-than sign and greater-than sign).

Example:

<p>

<p>: Defines a paragraph.

 

HTML5 Document

Creating an example HTML5 code that includes every possible HTML5 tag would be quite extensive, but I can provide a comprehensive example that covers most of the commonly used HTML5 tags. This will give you a broad overview of HTML5 elements.  I will explain the tags in more detail later. Here's an example:


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>HTML5 Example</title>
    <link rel="stylesheet" href="/LB/styles.css">
</head>
<body>
    <!-- Header and Navigation -->
    <header>
        <h1>Welcome to the HTML5 Example Page</h1>
        <nav>
            <ul>
                <li><a href="#section1">Section 1</a></li>
                <li><a href="#section2">Section 2</a></li>
                <li><a href="#section3">Section 3</a></li>
                <li><a href="#contact">Contact</a></li>
            </ul>
        </nav>
    </header>

    <!-- Section 1: Introduction -->
    <section id="section1">
        <h2>Introduction</h2>
        <p>This is a sample paragraph demonstrating <strong>HTML5</strong> features.</p>
        <p>Here's an example of a <a href="https://www.example.com">link</a> to an external site.</p>
        <p>This is a <abbr title="Hypertext Markup Language">HTML</abbr> abbreviation.</p>
        <figure>
            <img src="/LB/image.jpg" alt="Sample Image">
            <figcaption>Figure 1: A sample image with caption.</figcaption>
        </figure>
        <mark>Highlighted text</mark> example.
    </section>

    <!-- Section 2: Multimedia -->
    <section id="section2">
        <h2>Multimedia</h2>
        <video controls>
            <source src="/LB/movie.mp4" type="video/mp4">
            Your browser does not support the video tag.
        </video>
        <audio controls>
            <source src="/LB/audio.mp3" type="audio/mp3">
            Your browser does not support the audio element.
        </audio>
    </section>

    <!-- Section 3: Form -->
    <section id="section3">
        <h2>Contact Form</h2>
        <form action="/submit" method="post">
            <label for="name">Name:</label>
            <input type="text" id="name" name="name" required>
            <label for="email">Email:</label>
            <input type="email" id="email" name="email" required>
            <label for="dob">Date of Birth:</label>
            <input type="date" id="dob" name="dob">
            <label for="color">Favorite Color:</label>
            <input type="color" id="color" name="color">
            <label for="file">Upload File:</label>
            <input type="file" id="file" name="file">
            <label for="range">Range:</label>
            <input type="range" id="range" name="range" min="0" max="100">
            <label for="message">Message:</label>
            <textarea id="message" name="message"></textarea>
            <button type="submit">Submit</button>
        </form>
    </section>

    <!-- Contact Info -->
    <footer id="contact">
        <address>
            <p>Contact us at:</p>
            <p>Email: <a href="mailto:This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.</a></p>
            <p>Phone: <a href="tel:+1234567890">+1234567890</a></p>
        </address>
        <p>&copy; 2024 HTML5 Example</p>
    </footer>

    <!-- Script -->
    <script src="/LB/scripts.js"></script>
</body>
</html>


This example includes a variety of HTML5 elements such as headers, sections, navigation, forms, multimedia, and more.

HTML5 Document Format

Comments

HTML5 documents usually start with comments from the developer/s. Here's the HTML code with comments explaining each tag:

<!-- This is an HTML5 comment. -->
An HTML5 comment starts with the less-than sign an exclamation point, and two dashes (<!--) and ends with two dahses and a greater-than sign (-->).

<!DOCTYPE html>
<!-- The DOCTYPE declaration defines the document type and version of HTML. In this case, it's HTML5. -->

<html lang="en">
<!-- The <html> element is the root element of an HTML document. The lang attribute specifies the language of the document. -->

<head>
<!-- The <head> element contains meta-information about the document, such as its title and links to scripts and stylesheets. -->

<meta charset="UTF-8">
<!-- The <meta charset="UTF-8"> element specifies the character encoding for the document, ensuring it can handle text in various languages. -->

<meta name="viewport" content="width=device-width, initial-scale=1.0">
<!-- The <meta name="viewport"> element controls the layout on mobile browsers, setting the width to the device width and scaling the page to a reasonable size. -->

<title>HTML5 Example</title>
<!-- The <title> element sets the title of the document, which is displayed in the browser's title bar or tab. -->

<link rel="stylesheet" href="/LB/styles.css">
<!-- The <link> element defines the relationship between the current document and an external resource. In this case, it's linking to an external CSS file for styling the page. -->

</head>
/ (backslash) and the tag name ends the tag;

Additional Insights

HTML5 comments are used to leave notes or explanations in the code, which can help developers understand the purpose and structure of the code. Comments are not rendered by the browser, so they do not affect the visual presentation of the webpage. Here are some best practices for using HTML5 comments:

1. Basic Syntax

HTML comments start with <!-- and end with -->. Everything between these markers is treated as a comment.

<!-- This is a comment -->
<p>This is a paragraph.</p>

2. Explaining Code Sections

Use comments to explain the purpose of different sections of your HTML document. This helps other developers (and yourself) understand the structure and intent of the code.

<!-- Main navigation bar -->
<nav>
    <ul>
        <li><a href="#home">Home</a></li>
        <li><a href="#about">About</a></li>
        <li><a href="#contact">Contact</a></li>
    </ul>
</nav>

3. Marking TODOs and FIXMEs

Use comments to mark sections of the code that need further work or review.

<!-- TODO: Update the link to the latest version -->
<a href="https://example.com/download">Download</a>

<!-- FIXME: Correct the alignment issue in the footer -->
<footer>
    <p>Footer content</p>
</footer>

4. Temporarily Disabling Code

Comments can be used to temporarily disable code that you don't want to delete but want to prevent from rendering or executing.

<!--
<div class="advertisement">
    <p>Ad content here</p>
</div>
-->

5. Section Headers

Use comments to create clear section headers, especially in long documents. This makes it easier to navigate the code.

<!-- ===================== -->
<!--   Header Section       -->
<!-- ===================== -->
<header>
    <h1>Website Title</h1>
</header>

6. Inline Comments

Provide context for specific lines or small sections of code.

<p>This is a paragraph.</p> <!-- This paragraph is for introductory text -->

7. Avoiding Overuse

While comments are useful, over-commenting can clutter the code. Ensure comments add value and avoid stating the obvious.

<!-- Good Comment: Explains why something is done -->
<p>Price: $9.99</p> <!-- Displaying the product price -->

<!-- Bad Comment: Redundant comment -->
<p>Price: $9.99</p> <!-- This is a paragraph -->

8. Consistency

Be consistent with your commenting style throughout the document. This includes the format, capitalization, and punctuation of comments.

<!-- Main Content Section -->
<section>
    <!-- Article 1 -->
    <article>
        <h2>Article Title</h2>
        <p>Article content...</p>
    </article>
</section>

Example Combining Best Practices

Here's an example HTML document demonstrating various commenting practices:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Commented HTML5 Example</title>
    <link rel="stylesheet" href="/LB/styles.css">
</head>
<body>
    <!-- Header Section -->
    <header>
        <h1>My Website</h1>
        <!-- Main navigation -->
        <nav>
            <ul>
                <li><a href="#home">Home</a></li>
                <li><a href="#about">About</a></li>
                <li><a href="#services">Services</a></li>
                <li><a href="#contact">Contact</a></li>
            </ul>
        </nav>
    </header>

    <!-- Main Content Section -->
    <main>
        <!-- Introduction -->
        <section id="home">
            <h2>Welcome to My Website</h2>
            <p>This website provides information about my services.</p>
        </section>

        <!-- About Section -->
        <section id="about">
            <h2>About Me</h2>
            <p>Details about my background and experience.</p>
        </section>

        <!-- Services Section -->
        <section id="services">
            <h2>Services</h2>
            <p>Overview of the services I offer.</p>
        </section>

        <!-- Contact Section -->
        <section id="contact">
            <h2>Contact</h2>
            <form>
                <!-- Name Input -->
                <label for="name">Name:</label>
                <input type="text" id="name" name="name">
                
                <!-- Email Input -->
                <label for="email">Email:</label>
                <input type="email" id="email" name="email">
                
                <!-- Message Input -->
                <label for="message">Message:</label>
                <textarea id="message" name="message"></textarea>
                
                <!-- Submit Button -->
                <button type="submit">Send</button>
            </form>
        </section>
    </main>

    <!-- Footer Section -->
    <footer>
        <p>&copy; 2024 My Website</p>
    </footer>
</body>
</html>

By following these practices, you can create well-documented and maintainable HTML5 code.

 

Evolution of the <!DOCTYPE html> Declaration

The <!DOCTYPE> declaration is an instruction to the web browser about what version of HTML the page is written in. Its primary purpose is to ensure that the web page is rendered correctly across different browsers and their various versions. Over time, the <!DOCTYPE> declaration has evolved, becoming simpler and more concise with the advent of HTML5.

Early HTML Versions

In the earlier versions of HTML, the <!DOCTYPE> declaration was more complex and verbose, specifying the Document Type Definition (DTD) which describes the rules for the HTML version being used. This ensured that the browser would parse the document correctly according to the specified standards.

HTML 2.0 (1995)

<!DOCTYPE html PUBLIC "-//IETF//DTD HTML 2.0//EN">

HTML 3.2 (1997)

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">

HTML 4.01 (1999) HTML 4.01 introduced three types of DTDs: Strict, Transitional, and Frameset.

Strict DTD: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
Transitional DTD: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
Frameset DTD: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">

These lengthy declarations provided detailed instructions about the document's structure and the rules that the browser should follow when rendering the content.

XHTML 1.0 (2000)

XHTML, a stricter and more XML-based version of HTML, also had similar lengthy <!DOCTYPE> declarations.

XHTML 1.0 Strict: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

XHTML 1.0 Transitional: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
XHTML 1.0 Frameset: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">

HTML5 (2014)

With the introduction of HTML5, the <!DOCTYPE> declaration was greatly simplified. The new declaration is short, easy to remember, and does not reference a specific DTD. This simplification was part of the effort to make HTML more accessible and easier to use.

<!DOCTYPE html>

Summary

The evolution of the <!DOCTYPE> declaration reflects the broader trend in web development towards simplicity and ease of use. The lengthy and complex declarations of the past were necessary to ensure proper rendering and adherence to standards. However, as browsers and standards evolved, a simpler and more universal declaration became possible, culminating in the concise <!DOCTYPE html> of HTML5. This change has made it easier for developers to write and maintain web pages while ensuring compatibility across different browsers.

 

Tags

In HTML, tags are used to mark up the start and end of an element. The forward slash / is used within the closing tag to indicate the end of that element. Here’s how it works:

  1. Opening Tag:
    • The opening tag starts the element and is written with the element name enclosed in angle brackets.
    • Example: <div>
  2. Closing Tag:
    • The closing tag ends the element and is written with a forward slash / followed by the element name, enclosed in angle brackets.
    • Example: </div>
  3. Self-Closing Tags: Some tags like <meta>, <link>, and <img> can be self-closing, meaning they don't require a separate closing tag. These are written as <tagname /> in XHTML, but in HTML5, the self-closing form <tagname> without a closing tag is also valid.

Here is a comprehensive list of HTML5 tags along with their meanings:

Document Metadata

  • <!DOCTYPE>: Defines the document type and version.
  • <html>: The root element of an HTML document.
  • <head>: Contains meta-information about the document.
  • <title>: Sets the title of the document shown in the browser title bar or tab.
  • <meta>: Provides metadata such as document description, character set, keywords, etc.
  • <link>: Links the document to external resources like stylesheets.
  • <style>: Contains internal CSS styles.
  • <script>: Embeds or references executable code (JavaScript).
  • <base>: Sets the base URL for all relative URLs in the document.

Content Sectioning

  • <body>: Contains the content of an HTML document.
  • <header>: Represents introductory content, typically a group of introductory or navigational aids.
  • <nav>: Defines navigation links.
  • <section>: Defines a section in a document.
  • <article>: Represents a self-contained composition in a document.
  • <aside>: Represents content aside from the main content, like sidebars.
  • <footer>: Represents a footer for its nearest sectioning content or sectioning root element.
  • <h1> to <h6>: Define headings, <h1> being the highest (most important) and <h6> the lowest (least important).

Text Content

  • <p>: Defines a paragraph.
  • <hr>: Represents a thematic break between paragraph-level elements.
  • <pre>: Represents preformatted text.
  • <blockquote>: Defines a section that is quoted from another source.
  • <ol>: Defines an ordered list.
  • <ul>: Defines an unordered list.
  • <li>: Defines a list item.
  • <dl>: Defines a description list.
  • <dt>: Defines a term in a description list.
  • <dd>: Defines a description of a term in a description list.
  • <figure>: Represents self-contained content, like illustrations, diagrams, photos, etc.
  • <figcaption>: Defines a caption for a <figure> element.
  • <div>: Defines a division or section in a document.

Inline Text Semantics

  • <a>: Defines a hyperlink.
  • <em>: Defines emphasized text.
  • <strong>: Defines important text.
  • <small>: Defines smaller text.
  • <s>: Defines text that is no longer correct.
  • <cite>: Defines a citation.
  • <q>: Defines a short inline quotation.
  • <dfn>: Represents the defining instance of a term.
  • <abbr>: Defines an abbreviation.
  • <time>: Defines a specific time (or datetime).
  • <code>: Defines a piece of computer code.
  • <var>: Defines a variable.
  • <samp>: Defines sample output from a computer program.
  • <kbd>: Defines keyboard input.
  • <sub>: Defines subscript text.
  • <sup>: Defines superscript text.
  • <i>: Defines a part of text in an alternate voice or mood.
  • <b>: Defines bold text.
  • <u>: Defines text that should be stylistically different from normal text.
  • <mark>: Defines marked/highlighted text.
  • <ruby>: Defines a ruby annotation (for East Asian typography).
  • <rt>: Defines the explanation/pronunciation of characters in a ruby annotation.
  • <rp>: Provides fallback for browsers that do not support ruby annotations.
  • <bdi>: Isolates a part of text that might be formatted in a different direction from other text outside it.
  • <bdo>: Overrides the current text direction.
  • <span>: Used to group inline-elements in a document.
  • <br>: Produces a line break in text.
  • <wbr>: Defines a possible line-break.

Image and Multimedia

  • <img>: Embeds an image in the document.
  • <iframe>: Embeds another HTML page within the current page.
  • <embed>: Embeds external content at the specified point in the document.
  • <object>: Defines an embedded object.
  • <param>: Defines parameters for an <object> element.
  • <video>: Embeds a video.
  • <audio>: Embeds sound content.
  • <source>: Specifies multiple media resources for <video> and <audio>.
  • <track>: Defines text tracks for <video> and <audio> elements.

Embedded Content

  • <canvas>: Used to draw graphics via scripting (usually JavaScript).
  • <map>: Defines an image map (a clickable area within an image).
  • <area>: Defines a clickable area within an image map.
  • <svg>: Defines SVG graphics.
  • <math>: Embeds mathematical notation in a document.

Scripting

  • <script>: Embeds or references executable code (JavaScript).
  • <noscript>: Defines an alternate content for users that do not support client-side scripts.

Demarcating Edits

  • <ins>: Defines a text that has been inserted into a document.
  • <del>: Defines a text that has been deleted from a document.

Table Content

  • <table>: Defines a table.
  • <caption>: Defines a table caption.
  • <thead>: Groups the header content in a table.
  • <tbody>: Groups the body content in a table.
  • <tfoot>: Groups the footer content in a table.
  • <tr>: Defines a row in a table.
  • <th>: Defines a header cell in a table.
  • <td>: Defines a cell in a table.
  • <col>: Specifies column properties for each column within a <colgroup> element.
  • <colgroup>: Specifies a group of one or more columns in a table for formatting.

Forms

  • <form>: Defines an HTML form for user input.
  • <label>: Defines a label for an <input> element.
  • <input>: Defines an input control.
  • <button>: Defines a clickable button.
  • <select>: Defines a drop-down list.
  • <optgroup>: Defines a group of related options in a drop-down list.
  • <option>: Defines an option in a drop-down list.
  • <textarea>: Defines a multi-line text input control.
  • <fieldset>: Groups related elements in a form.
  • <legend>: Defines a caption for a <fieldset> element.
  • <datalist>: Specifies a list of pre-defined options for input controls.
  • <output>: Represents the result of a calculation or user action.
  • <progress>: Represents the completion progress of a task.
  • <meter>: Represents a scalar measurement within a known range.

Interactive Elements

  • <details>: Defines additional details that the user can view or hide.
  • <summary>: Defines a visible heading for a <details> element.
  • <dialog>: Defines a dialog box or other interactive component.

These tags form the building blocks of HTML5, each with specific functions and purposes to create structured and semantically meaningful web content.

Detailed Example

<!DOCTYPE html>
<!-- Opening and closing of the document type declaration; no closing tag is needed -->

<html lang="en">
<!-- Opening tag for the HTML document with a language attribute -->

<head>
<!-- Opening tag for the head section -->

    <meta charset="UTF-8">
    <!-- Self-closing tag for meta information; no closing tag is needed -->

    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <!-- Self-closing tag for viewport settings; no closing tag is needed -->

    <title>HTML5 Example</title>
    <!-- Opening and closing tags for the document title -->

    <link rel="stylesheet" href="/LB/styles.css">
    <!-- Self-closing tag linking to an external stylesheet; no closing tag is needed -->

</head>
<!-- Closing tag for the head section -->

<body>
<!-- Opening tag for the body section -->

    <h1>Welcome to the HTML5 Example Page</h1>
    <!-- Opening and closing tags for an H1 header element -->

</body>
<!-- Closing tag for the body section -->

</html>
<!-- Closing tag for the HTML document -->

Key Points:

  • HTML Comments: Begin with <!-- and end with -->. They are used to include notes or explanations in the code.
  • <!DOCTYPE html>: The DOCTYPE declaration defines the document type and version of HTML. For HTML5, it is simply <!DOCTYPE html>.
  • Root Element (<html>): The <html> tag encloses all the content of an HTML document. The lang attribute specifies the language.
  • Document Metadata (<head>): The <head> tag contains meta-information such as the document's title, character set, and links to external resources.
  • Document Body (<body>): The <body> tag contains the content of the HTML document, including text, images, links, and other elements.
  • Content Sections: Tags like <header>, <nav>, <section>, <main>, and <footer> help organize content into meaningful sections.
  • Forms and Interactive Elements: Tags like <form>, <input>, <textarea>, and <button> are used to create interactive forms for user input.

This explanation provides a clear understanding of the purpose and structure of each tag used in an HTML5 document.