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    HTML coding standard

    Document Properties

    • Use the HTML5 Doctype and HTML5 features
    Good
    <!DOCTYPE html>
    • Do NOT include xml namespace in the document.
    Bad  
    <html xmlns="http://www.w3.org/1999/xhtml">
    • Character Encoding: All markup should be delivered via the following HTML element as UTF-8, as it is the most friendly for internationalization.
    Good
    <meta charset="utf-8">
    • Responsiveness: The following tag should be added in order to support mobile browsing.
    Good
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    • Indentation: Indentation should be 2 spaces for html files. Spaces should be used instead of tab.

    • Readability vs Compression: We prefer readability over file-size savings when it comes to maintaining existing files. Plenty of whitespace is encouraged, along with ASCII art, where appropriate. There is no need for any developer to purposefully compress HTML or CSS, nor obfuscate JavaScript.

    • Markup and inline styling: Markup defines the structure and outline of a document and offers a structured content. It is not intended to define the look and feel of the content on the page beyond rudimentary concepts such as headers, paragraphs, and lists. The presentation attributes of HTML have all been deprecated and style should be contained in style sheets. Inline styling should not be used, and should be minimized if its usage is really necessary.

    • General structure for HTML document:

      <!DOCTYPE html>
      <html>
      <head>
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">

      <title>CS2103/T (Module website)</title>

      <!-- Sample stylesheet inclusion -->
      <link type="text/css" href="styles/common.css" rel="stylesheet">
      </head>
      <body>
      <!-- Body content goes here -->

      <!-- Sample javascript inclusion -->
      <script type="text/javascript" src="/js/jquery-minified.js"></script>
      </body>
      </html>

    Tags

    • All HTML tags are to be closed properly.
    Good
    <div>Stuff</div>
    Bad  
    <p>Stuff
    <p>More Stuff
    • Do not use /> for void elements.
      Example of void elements are: br, img, link, meta. The full list of HTML void elements can be accessed here.
    Good
    <br>
    <img src="a" width="5px" height="10px">
    Bad  
    <br />
    <img src="a" width="5px" height="10px" />
    • Use lowercase for all attributes and tag names.
    Good
    <div id="frame">Test</div>
    Bad  
    <DIV ID="frame">Test</div>

    Attributes

    • Use attr="value" for attribute values.
    Good
    <input value="computer" id="some-input" disabled="disabled" tabindex="2">
    Bad  
    <!-- single/no quotes -->
    <input value=computer id='some-input' disabled='disabled' tabindex=2>

    <!-- specify boolean variables in the attributes -->
    <input value="computer" id="some-input" disabled tabindex="2">

    Naming

    • Classes: See CSS Style Guide.
    • IDs: lower-case, join-by-hyphen. e.g., header-content-week3

    Indentation

    • Indentation should be 2 spaces for HTML files (not 4).
    • Spaces should be used instead of tab.

    Miscellaneous

    • Follow this format for script tags:
    Good
    <script type="text/javascript" src="/js/jquery-minified.js"></script>
    Bad  
    <script language="JavaScript" src="/js/jquery-minified.js"></script>
    • Do not have trailing whitespaces between opening and closing tags. However, line breaks and indentation are encouraged if it enhances readability.
    Good
    <p>Student Name</p>
    <p>
    Lorem ipsum dolor sit amet, consectetur adipiscing elit,
    sed do eiusmod tempor incididunt ut labore
    et dolore magna aliqua. Ut enim ad minim veniam,
    </p>
    Bad  
    <p> Student Name </p>
    • Include rel="noopener noreferrer" when using target="_blank" in links.

      RATIONALE: Leaving this out would enable attackers to get hold of window.opener object, which can be used to redirect to a malicious link. [Source]

    Good
    <a target="_blank" rel="noopener noreferrer" href="https://example.com">Example.com</a>
    Bad  
    <a target="_blank" href="https://example.com">Example.com</a>