Why are my nested ordered lists displaying incorrect numbering in HTML and CSS, and how can I fix it?

Nested Ordered Lists with Incorrect Numbering

This issue arises when creating nested ordered lists using HTML and CSS. The following code is used:

ol {
    counter-reset: item;
    padding-left: 10px;
}
li {
    display: block
}
li:before {
    content: counters(item, ".") " ";
    counter-increment: item
}

<ol>
    <li>one</li>
    <li>two</li>
    <ol>
        <li>two.one</li>
        <li>two.two</li>
        <li>two.three</li>
    </ol>
    <li>three</li>
    <ol>
        <li>three.one</li>
        <li>three.two</li>
        <ol>
            <li>three.two.one</li>
            <li>three.two.two</li>
        </ol>
    </ol>
    <li>four</li>
</ol>

Incorrect Output:

The expected output should resemble:

1. one
2. two
  2.1. two.one
  2.2. two.two
  2.3. two.three
3. three
  3.1 three.one
  3.2 three.two
    3.2.1 three.two.one
    3.2.2 three.two.two
4. four

However, the actual outcome displays incorrect numbering:

1. one
2. two
  2.1. two.one
  2.2. two.two
  2.3. two.three
2.4 three
  2.1 three.one
  2.2 three.two
    2.2.1 three.two.one
    2.2.2 three.two.two
2.3 four

Solutions:

To resolve this issue, two solutions are available:

1. Disable "Normalize CSS" in JSFiddle. This option defaults all list margins and paddings to 0.
2. Include sub-lists within the main
3. elements, as shown below:

ol {
  counter-reset: item
}
li {
  display: block
}
li:before {
  content: counters(item, ".") " ";
  counter-increment: item
}

<ol>
  <li>one</li>
  <li>two
    <ol>
      <li>two.one</li>
      <li>two.two</li>
      <li>two.three</li>
    </ol>
  </li>
  <li>three
    <ol>
      <li>three.one</li>
      <li>three.two
        <ol>
          <li>three.two.one</li>
          <li>three.two.two</li>
        </ol>
      </li>
    </ol>
  </li>
  <li>four</li>
</ol>

Once implemented, the ordered lists will display the correct numbering as intended.

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