Build a Technical Documentation Page

Hello, i’m failing with “You should have the same number of .nav-link and .main-section elements.”. I rechecked everything and everything is matching by the number count. I have spent the last hour to find the mistake but whether im stupid or blind, but i can’t find it.

<!DOCTYPE hmtl>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<title>JS Documentation></title>
<link rel="stylesheet" href="styles.css" />
</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>
            </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-base
                             d 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:</p>
          <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 broswer
</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> ley 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>
<p>However, object attributes are not protected, 
  so the following statement is executed without problems.</p>
  <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>Booleam. 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>
           <p>and Object</p>
           </ul>

           <p>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.</p>
                 </article>
           </section>


           <section class="main-section" id="if...else_statement">
             <header>if...else statement</header>
             <article>
             <p>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:</p>
                 <code>if (condition) { statement_1; } else { statement_2; }</code>
                 <p>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>
                       <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>
<p>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:
     </p>
     <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>
<p>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:
     </p>
     <code>if (x = y) { /* statements here */ }</code>
     <p>If you need to use an assignment in a conditional expression,
        a common practice is to put additional parentheses around
         the assignment. For example:</p>
         <code>if ((x = y)) { /* statements here */ }</code>
         </article>
         </section>

         <section class="main-section" id="while_statement">
           <header>while statement</header>
           <article>
           <p>A while statement executes its statements as
              long as a specified condition evaluates to true.
               A while statement looks as follows:</p>
               <code>while (condition) statement</code>
               <p>If the condition becomes false, statement within
                  the loop stops executing and control passes
                   to the statement following the loop.</p>
                   <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 < 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 first pass: n = 2 and x = 3</li>
                            <li>After the first pass: n = 3 and x = 6</li>
                            </ul>
                            <p>After completing the third pass,
                               the condition n < 3 is no longer true, 
                               so the loop terminates.</p>
                               </article>
                               </section>
                      
                      <section="main-section" id="Function_declarations">
                        <header>Function declarations</header>
                        <article>
                        <p>A function definition (also called a function declaration,
                           or function statement) consists of the function keyword,
                            followed by:</p>
                            <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>
                                           <ul>
                                             <li>All the documentation in this page is taken from <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide" target="_blank">MDN</a>
                                             </li>
                                             </ul>
                                             </section>
                                             </main>
                                             </body>    
                   
  </html>

Hello. On the section element before your last, that is, your 13th section element, you have forgotten to include the class attribute. Your code reads <section=main-section...> which is unrecognizable as it is incorrect syntax. This is why you get that error, one of your sections is not recognized and therefore not counted.

Hey! Thanks a lot for the help!

No problem, happy to help!