HTML and CSS lesson 11: Classes, ids and which rule wins

US version. US grades and US spelling. · UK version of this lesson

Classes (.note) style chosen elements; ids (#intro) name one element. When rules clash, the more specific selector wins: id beats class, class beats tag name. A complete 40-minute HTML and CSS lesson for beginners (Grades 6–7), from Unit 4: CSS: style rules. You build real web pages right here in your browser – nothing to install.

Time: 40 minutes + 20 min homework
Grade: Grades 6–7 (ages 11–12)
You need: A computer or tablet, paper and a pencil
Graded: Instantly, with explanations

For parents: how to use this lesson

You don't need to know HTML yourself. The lesson explains each step on screen, the way Mr Babbage, our Head of Computing, likes it: a worked example first, then a go for your child. When your child builds a page, the browser draws it straight away and Classfern grades it with a checklist.

Read what your child will learn together.
Press Start the lesson below. Sit with your child for the teaching and the worked example (about 15 minutes): ask them to point at each tag and say what it does.
Let them do the practice on their own. If a page doesn't look right, the checklist says what is missing – let them find the mistake before you help.
Finish with the exit questions and the talk question: “When would you use a class instead of an id?”
Later that day or the next day: the homework (20 minutes), then a practice test.

Watch out for

The last rule always wins. Specificity comes first; order only decides between equals.
#note selects class="note". A hash selects an id; use .note for a class.

Miss Lovelace's tip for home: ask your child to change one thing on their page – a word, a color, a size – and predict what will happen before they look. Predicting first is how programmers learn fastest.

What your child will learn

Learning goal: style elements with a class selector.

Success looks like

I can style elements with a class selector.
I can use an id for one element.
I can work out which rule wins.

Key words

class · id · class selector · id selector · specificity · cascade · inline style

What to have ready

A device with a web browser (pages are built and checked right in the browser – nothing to install)
Paper for planning and sketching
A keyboard helps for typing code (a tablet works too)

The big ideas (for the adult)

To style only SOME paragraphs, give them a class: <p class="note">. The CSS selector for a class starts with a dot: .note { … }. Many elements can share a class, and one element can have several classes.

An id names exactly ONE element: <p id="intro">, selected with a hash: #intro. Use classes for styling most things; ids are for one-off elements.

When rules clash, the browser checks specificity first: an id is more specific than a class, and a class is more specific than a tag name. Only if two rules are equally specific does the later one win. A style="…" attribute on an element beats them all – which is why it is best used rarely.

Worked example: a class

CSS:

.note { color: purple; }

HTML:

<p>Normal text.</p>
<p class="note">This note is purple.</p>

The lesson, step by step

40 minutes in 5 parts
Part	Time	How it is checked
Starter	5 min	Graded by Classfern
Learn	8 min	Read, watch and talk
See it	7 min	Graded by Classfern
Practice	15 min	Graded by Classfern
Check and reflect	5 min	Graded by Classfern + self-check

The lesson

It runs here on the page. No sign-up and no names – nothing you type is sent anywhere. Each visit picks a new mix of questions.

Homework

20 minutes: predict what the browser will do, build or fix a short page, and check the key ideas – then a short reflection. New questions every time, all graded instantly.

Practice tests

All computer science practice tests · All 20 HTML and CSS lessons

Curriculum

CSTA K–12 Computer Science Standards (2017), grades 6–8: 2-AP-17 – Systematically test and refine programs using a range of test cases.

The standard codes are CSTA's; the descriptions are our own words.

Our lessons and questions are our own. They are not written or endorsed by any government department, testing agency or exam board. HTML and CSS are open web standards; Classfern is not affiliated with the organisations that publish them.