Technical Documentation Page.hey..what is my problem? the error said:Your Technical Documentation project should use at least one media query

    <head>
        <meta charset="utf-8">
        <meta name="viewport"  content="width=device-width , initial-scale=1.0">
        <link href="styles.css" rel="stylsheet">
    </head>
   <body>
<nav id="navbar">
  <header>JS Documentation</header>
  <ul>
    <li><a class="nav-link" href="#Introduction">Introduction</a></li>
    <li>
      <a class="nav-link" href="#What_you_should_already_know">What you should already know</a>
    </li>
    <li>
      <a class="nav-link" href="#JavaScript_and_Java">JavaScript and Java</a>
    </li>
    <li><a class="nav-link" href="#Hello_world">Hello world</a></li>
    <li><a class="nav-link" href="#Variables">Variables</a></li>
    <li>
      <a class="nav-link" href="#Declaring_variables">Declaring variables</a>
    </li>
    <li><a class="nav-link" href="#Variable_scope">Variable scope</a></li>
    <li>
      <a class="nav-link" href="#Global_variables">Global variables</a>
    </li>
    <li><a class="nav-link" href="#Constants">Constants</a></li>
    <li><a class="nav-link" href="#Data_types">Data types</a></li>
    <li>
      <a class="nav-link" href="#if...else_statement">if...else statement</a>
    </li>
    <li><a class="nav-link" href="#while_statement">while statement</a></li>
    <li>
      <a class="nav-link" href="#Function_declarations">Function declarations</a>
    </li>
    <li><a class="nav-link" href="#Reference">Reference</a></li>
  </ul>
</nav>
<main id="main-doc">
  <section class="main-section" id="Introduction">
    <header>Introduction</header>
    <article>
      <p>
        JavaScript is a cross-platform, object-oriented scripting language.
        It is a small and lightweight language. Inside a host environment
        (for example, a web browser), JavaScript can be connected to the
        objects of its environment to provide programmatic control over
        them.
      </p>

      <p>
        JavaScript contains a standard library of objects, such as Array,
        Date, and Math, and a core set of language elements such as
        operators, control structures, and statements. Core JavaScript can
        be extended for a variety of purposes by supplementing it with
        additional objects; for example:
      </p>
      <ul>
        <li>
          Client-side JavaScript extends the core language by supplying
          objects to control a browser and its Document Object Model (DOM).
          For example, client-side extensions allow an application to place
          elements on an HTML form and respond to user events such as mouse
          clicks, form input, and page navigation.
        </li>
        <li>
          Server-side JavaScript extends the core language by supplying
          objects relevant to running JavaScript on a server. For example,
          server-side extensions allow an application to communicate with a
          database, provide continuity of information from one invocation to
          another of the application, or perform file manipulations on a
          server.
        </li>
      </ul>
    </article>
  </section>
  <section class="main-section" id="What_you_should_already_know">
    <header>What you should already know</header>
    <article>
      <p>This guide assumes you have the following basic background:</p>

      <ul>
        <li>
          A general understanding of the Internet and the World Wide Web
          (WWW).
        </li>
        <li>Good working knowledge of HyperText Markup Language (HTML).</li>
        <li>
          Some programming experience. If you are new to programming, try
          one of the tutorials linked on the main page about JavaScript.
        </li>
      </ul>
    </article>
  </section>
  <section class="main-section" id="JavaScript_and_Java">
    <header>JavaScript and Java</header>
    <article>
      <p>
        JavaScript and Java are similar in some ways but fundamentally
        different in some others. The JavaScript language resembles Java but
        does not have Java's static typing and strong type checking.
        JavaScript follows most Java expression syntax, naming conventions
        and basic control-flow constructs which was the reason why it was
        renamed from LiveScript to JavaScript.
      </p>

      <p>
        In contrast to Java's compile-time system of classes built by
        declarations, JavaScript supports a runtime system based on a small
        number of data types representing numeric, Boolean, and string
        values. JavaScript has a prototype-based object model instead of the
        more common class-based object model. The prototype-based model
        provides dynamic inheritance; that is, what is inherited can vary
        for individual objects. JavaScript also supports functions without
        any special declarative requirements. Functions can be properties of
        objects, executing as loosely typed methods.
      </p>
      <p>
        JavaScript is a very free-form language compared to Java. You do not
        have to declare all variables, classes, and methods. You do not have
        to be concerned with whether methods are public, private, or
        protected, and you do not have to implement interfaces. Variables,
        parameters, and function return types are not explicitly typed.
      </p>
    </article>
  </section>
  <section class="main-section" id="Hello_world">
    <header>Hello world</header>
    <article>
      To get started with writing JavaScript, open the Scratchpad and write
      your first "Hello world" JavaScript code:
      <code>function greetMe(yourName) { alert("Hello " + yourName); }
        greetMe("World");
      </code>

      Select the code in the pad and hit Ctrl+R to watch it unfold in your
      browser!
    </article>
  </section>
  <section class="main-section" id="Variables">
    <header>Variables</header>
    <p>
      You use variables as symbolic names for values in your application.
      The names of variables, called identifiers, conform to certain rules.
    </p>
    <p>
      A JavaScript identifier must start with a letter, underscore (_), or
      dollar sign ($); subsequent characters can also be digits (0-9).
      Because JavaScript is case sensitive, letters include the characters
      "A" through "Z" (uppercase) and the characters "a" through "z"
      (lowercase).
    </p>
    <p>
      You can use ISO 8859-1 or Unicode letters such as å and ü in
      identifiers. You can also use the Unicode escape sequences as
      characters in identifiers. Some examples of legal names are
      Number_hits, temp99, and _name.
    </p>
  </section>
  <section class="main-section" id="Declaring_variables">
    <header>Declaring variables</header>
    <article>
      You can declare a variable in three ways:
      <p>
        With the keyword var. For example, <code>var x = 42.</code> This
        syntax can be used to declare both local and global variables.
      </p>
      <p>
        By simply assigning it a value. For example,
        <code>x = 42.</code> This always declares a global variable. It
        generates a strict JavaScript warning. You shouldn't use this
        variant.
      </p>
      <p>
        With the keyword let. For example,<code> let y = 13.</code> This
        syntax can be used to declare a block scope local variable. See
        Variable scope below.
      </p>
    </article>
  </section>
  <section class="main-section" id="Variable_scope">
    <header>Variable scope</header>
    <article>
      <p>
        When you declare a variable outside of any function, it is called a
        global variable, because it is available to any other code in the
        current document. When you declare a variable within a function, it
        is called a local variable, because it is available only within that
        function.
      </p>

      <p>
        JavaScript before ECMAScript 2015 does not have block statement
        scope; rather, a variable declared within a block is local to the
        function (or global scope) that the block resides within. For
        example the following code will log 5, because the scope of x is the
        function (or global context) within which x is declared, not the
        block, which in this case is an if statement.
      </p>
      <code>if (true) { var x = 5; } console.log(x); // 5</code>
      <p>
        This behavior changes, when using the let declaration introduced in
        ECMAScript 2015.
      </p>

      <code>if (true) { let y = 5; } console.log(y); // ReferenceError: y is
        not defined</code>
    </article>
  </section>
  <section class="main-section" id="Global_variables">
    <header>Global variables</header>
    <article>
      <p>
        Global variables are in fact properties of the global object. In web
        pages the global object is window, so you can set and access global
        variables using the window.variable syntax.
      </p>

      <p>
        Consequently, you can access global variables declared in one window
        or frame from another window or frame by specifying the window or
        frame name. For example, if a variable called phoneNumber is
        declared in a document, you can refer to this variable from an
        iframe as parent.phoneNumber.
      </p>
    </article>
  </section>
  <section class="main-section" id="Constants">
    <header>Constants</header>
    <article>
      <p>
        You can create a read-only, named constant with the const keyword.
        The syntax of a constant identifier is the same as for a variable
        identifier: it must start with a letter, underscore or dollar sign
        and can contain alphabetic, numeric, or underscore characters.
      </p>

      <code>const PI = 3.14;</code>
      <p>
        A constant cannot change value through assignment or be re-declared
        while the script is running. It has to be initialized to a value.
      </p>

      <p>
        The scope rules for constants are the same as those for let block
        scope variables. If the const keyword is omitted, the identifier is
        assumed to represent a variable.
      </p>

      <p>
        You cannot declare a constant with the same name as a function or
        variable in the same scope. For example:
      </p>

      <code>// THIS WILL CAUSE AN ERROR function f() {}; const f = 5; // THIS
        WILL CAUSE AN ERROR ALSO function f() { const g = 5; var g;
        //statements }</code>
      However, object attributes are not protected, so the following
      statement is executed without problems.
      <code>const MY_OBJECT = {"key": "value"}; MY_OBJECT.key =
        "otherValue";</code>
    </article>
  </section>
  <section class="main-section" id="Data_types">
    <header>Data types</header>
    <article>
      <p>The latest ECMAScript standard defines seven data types:</p>
      <ul>
        <li>
          <p>Six data types that are primitives:</p>
          <ul>
            <li>Boolean. true and false.</li>
            <li>
              null. A special keyword denoting a null value. Because
              JavaScript is case-sensitive, null is not the same as Null,
              NULL, or any other variant.
            </li>
            <li>
              undefined. A top-level property whose value is undefined.
            </li>
            <li>Number. 42 or 3.14159.</li>
            <li>String. "Howdy"</li>
            <li>
              Symbol (new in ECMAScript 2015). A data type whose instances
              are unique and immutable.
            </li>
          </ul>
        </li>

        <li>and Object</li>
      </ul>
      Although these data types are a relatively small amount, they enable
      you to perform useful functions with your applications. Objects and
      functions are the other fundamental elements in the language. You can
      think of objects as named containers for values, and functions as
      procedures that your application can perform.
    </article>
  </section>
  <section class="main-section" id="if...else_statement">
    <header>if...else statement</header>
    <article>
      Use the if statement to execute a statement if a logical condition is
      true. Use the optional else clause to execute a statement if the
      condition is false. An if statement looks as follows:

      <code>if (condition) { statement_1; } else { statement_2; }</code>
      condition can be any expression that evaluates to true or false. See
      Boolean for an explanation of what evaluates to true and false. If
      condition evaluates to true, statement_1 is executed; otherwise,
      statement_2 is executed. statement_1 and statement_2 can be any
      statement, including further nested if statements.
      <p>
        You may also compound the statements using else if to have multiple
        conditions tested in sequence, as follows:
      </p>
      <code>if (condition_1) { statement_1; } else if (condition_2) {
        statement_2; } else if (condition_n) { statement_n; } else {
        statement_last; }
      </code>
      In the case of multiple conditions only the first logical condition
      which evaluates to true will be executed. To execute multiple
      statements, group them within a block statement ({ ... }) . In
      general, it's good practice to always use block statements, especially
      when nesting if statements:

      <code>if (condition) { statement_1_runs_if_condition_is_true;
        statement_2_runs_if_condition_is_true; } else {
        statement_3_runs_if_condition_is_false;
        statement_4_runs_if_condition_is_false; }</code>
      It is advisable to not use simple assignments in a conditional
      expression, because the assignment can be confused with equality when
      glancing over the code. For example, do not use the following code:
      <code>if (x = y) { /* statements here */ }</code> If you need to use
      an assignment in a conditional expression, a common practice is to put
      additional parentheses around the assignment. For example:

      <code>if ((x = y)) { /* statements here */ }</code>
    </article>
  </section>
  <section class="main-section" id="while_statement">
    <header>while statement</header>
    <article>
      A while statement executes its statements as long as a specified
      condition evaluates to true. A while statement looks as follows:

      <code>while (condition) statement</code> If the condition becomes
      false, statement within the loop stops executing and control passes to
      the statement following the loop.

      <p>
        The condition test occurs before statement in the loop is executed.
        If the condition returns true, statement is executed and the
        condition is tested again. If the condition returns false, execution
        stops and control is passed to the statement following while.
      </p>

      <p>
        To execute multiple statements, use a block statement ({ ... }) to
        group those statements.
      </p>

      Example:

      <p>
        The following while loop iterates as long as n is less than three:
      </p>

      <code>var n = 0; var x = 0; while (n &lt; 3) { n++; x += n; }</code>
      <p>
        With each iteration, the loop increments n and adds that value to x.
        Therefore, x and n take on the following values:
      </p>

      <ul>
        <li>After the first pass: n = 1 and x = 1</li>
        <li>After the second pass: n = 2 and x = 3</li>
        <li>After the third pass: n = 3 and x = 6</li>
      </ul>
      <p>
        After completing the third pass, the condition n &lt; 3 is no longer
        true, so the loop terminates.
      </p>
    </article>
  </section>
  <section class="main-section" id="Function_declarations">
    <header>Function declarations</header>
    <article>
      A function definition (also called a function declaration, or function
      statement) consists of the function keyword, followed by:

      <ul>
        <li>The name of the function.</li>
        <li>
          A list of arguments to the function, enclosed in parentheses and
          separated by commas.
        </li>
        <li>
          The JavaScript statements that define the function, enclosed in
          curly brackets, { }.
        </li>
      </ul>
      <p>
        For example, the following code defines a simple function named
        square:
      </p>

      <code>function square(number) { return number * number; }</code>
      <p>
        The function square takes one argument, called number. The function
        consists of one statement that says to return the argument of the
        function (that is, number) multiplied by itself. The return
        statement specifies the value returned by the function.
      </p>
      <code>return number * number;</code>
      <p>
        Primitive parameters (such as a number) are passed to functions by
        value; the value is passed to the function, but if the function
        changes the value of the parameter, this change is not reflected
        globally or in the calling function.
      </p>
    </article>
  </section>
  <section class="main-section" id="Reference">
    <header>Reference</header>
    <article>
      <ul>
        <li>
          All the documentation in this page is taken from MDN
        </li>
      </ul>
    </article>
  </section>
</main>

I guess you need to add a media query to your stylesheet…

1 Like