CSS: ul, ol, li
  • ul means "Unordered List" and is a list that usually is denoted with bullets / circles (* syntax at start of line at Wikidot)
  • ol means "Ordered list" and is a list that usually is denoted with numbers (# syntax at start of line at Wikidot)

Furthermore:

  • li means "List Item" and surrounds each individual item. It tells the web browser (for example, Firefox) where to start each item in the list and where it ends.

Unordered Lists (ul)

Some Wikidot code:

* Test
* Hello ?
* This is the third item!

The same thing in HTML:
<ul>
    <li>Test</li>
    <li>Hello ?</li>
    <li>This is the third item!</li>
</ul>

And it appears on a page like this:
  • Test
  • Hello ?
  • This is the third item!

Ordered Lists (ol)

Some Wikidot code:

# Test
# Hello ?
# This is the third item!

The same thing in HTML:
<ol>
    <li>Test</li>
    <li>Hello ?</li>
    <li>This is the third item!</li>
</ol>

And it appears on a page like this:
  1. Test
  2. Hello ?
  3. This is the third item!

Lists embedded inside other lists (indented list items)

Does that help to explain?

Now, when you see something like this in the CSS:

#topbar ul li ul li {
    do: something;
}

That means you have one unordered list inside the other, like this:

Wikidot:

* First list
* First list still
 * Second, indented list (inside the other list)
* Back to first list again

HTML:
<ul>
    <li>First list</li>
    <li>First list still</li>
        <ul>
            <li>Second, indented list (inside the other list)</li>
        </ul>
    <li>Back to first list again</li>
</ul>

And on the rendered page:
  • First list
  • First list still
    • Second, indented list (inside the other list)
  • Back to first list again

So looking at the CSS again…

#topbar ul li ul li {
    do: something;
}

… you want to go to the top bar, then you're looking at the first ul item, then the next indented li, then an indented ul, etc. You end up affecting only the one labelled "Second, indented list (inside the other list)" in this example.
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