Class selectors in CSS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all elements with the class highlight.

CSS

.[1] { color: red; }

Drag options to blanks, or click blank then click option'

A*highlight

B#highlight

Chighlight

Dhighlighted

Attempts:

3 left

💡 Hint

Common Mistakes

Using a hash (#) instead of a dot (.) for class selectors.

Adding extra characters before the class name.

In CSS, a class selector starts with a dot (.) followed by the class name. Here, .highlight selects all elements with the class highlight.

2fill in blank

medium

Complete the code to make text bold for elements with the class bold-text.

CSS

.[1] { font-weight: bold; }

Drag options to blanks, or click blank then click option'

Abold-text

Btext-bold

Cboldtext

Dbold_text

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscores instead of hyphens.

Mixing up the order of words in the class name.

The class selector must exactly match the class name used in HTML. Here, .bold-text targets elements with class bold-text.

3fill in blank

hard

Fix the error in the class selector to change background color for container class.

CSS

[1]container { background-color: lightblue; }

Drag options to blanks, or click blank then click option'

A#

B.

C*

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using # instead of . for class selectors.

Omitting the dot before the class name.

Class selectors must start with a dot (.) before the class name. Here, .container correctly selects elements with class container.

4fill in blank

hard

Complete the code to select elements with class menu and set font size to 1.2rem.

CSS

[1]menu { font-size: 1.2rem; }

Drag options to blanks, or click blank then click option'

A.

B#

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using # instead of .

Adding colon (:) before class name.

In CSS, a class selector starts with a dot (.) immediately followed by the class name. Here, .menu selects all elements with the class menu.

5fill in blank

hard

Fill all three blanks to create a CSS rule that selects elements with class btn inside a nav element and sets their color to green.

CSS

[1]nav[2].[3]btn { color: green; }

Drag options to blanks, or click blank then click option'

A>

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or + combinators incorrectly.

Adding spaces between dot and class name.

To select elements with class btn inside a nav element, use nav .btn. The first blank is empty (no combinator) between nav and the space, the second blank is a space to separate nav and .btn, and the third blank is empty because the dot is already present before btn.

Practice

1. What does a CSS class selector start with to select elements by their class?

easy

A. A dot (.) before the class name

B. A hash (#) before the class name

C. No symbol, just the class name

D. An asterisk (*) before the class name

Solution

1. Step 1: Understand CSS selector symbols

   Class selectors always start with a dot (.) to target elements with that class.

2. Step 2: Compare with other selectors

   ID selectors use #, element selectors use no symbol, and * selects all elements.

3. Final Answer:

   A dot (.) before the class name -> Option A

4. Quick Check:

   Class selector = dot (.) [OK]

Hint: Class selectors always begin with a dot (.) [OK]

Common Mistakes:

• Using # instead of . for class selectors
• Omitting the dot before the class name
• Confusing class selectors with element selectors

2. Which of the following is the correct CSS syntax to style all elements with class highlight?

easy

A. highlight { color: red; }

B. #highlight { color: red; }

C. .highlight { color: red; }

D. *highlight { color: red; }

Solution

1. Step 1: Identify correct class selector syntax

   The class selector uses a dot (.) followed by the class name, so .highlight is correct.

2. Step 2: Check other options

   #highlight targets an ID, highlight alone targets elements named 'highlight', and *highlight is invalid syntax.

3. Final Answer:

   .highlight { color: red; } -> Option C

4. Quick Check:

   Class selector syntax = dot + class name [OK]

Hint: Remember: dot + class name for class selectors [OK]

Common Mistakes:

• Using # instead of . for classes
• Leaving out the dot before class name
• Confusing class selectors with element selectors

3. Given this HTML and CSS, what color will the text inside the <p> tag be?

<p class="note">Hello!</p>
.note { color: blue; }
.alert { color: red; }

medium

A. Red

B. Blue

C. Black (default)

D. No color applied

Solution

1. Step 1: Match class in HTML with CSS selector

   The <p> tag has class "note", so the CSS rule .note { color: blue; } applies.

2. Step 2: Check other CSS rules

   The .alert class styles red but does not apply here because the element does not have that class.

3. Final Answer:

   Blue -> Option B

4. Quick Check:

   Class matches CSS selector = blue text [OK]

Hint: Match class attribute with dot selector name [OK]

Common Mistakes:

• Confusing class names and applying wrong styles
• Ignoring that only matching classes apply styles
• Assuming default color when class is present

4. What is wrong with this CSS if you want to style elements with class menu?

menu { font-size: 1.2rem; }

medium

A. Font size value is invalid

B. Missing curly braces

C. Class name should be uppercase

D. Missing dot before class name

Solution

1. Step 1: Check selector syntax

   The selector menu targets elements named <menu>, not class "menu". Class selectors need a dot before the name.

2. Step 2: Verify other parts

   Curly braces and font size are correct. Class names are case-sensitive but lowercase is valid.

3. Final Answer:

   Missing dot before class name -> Option D

4. Quick Check:

   Class selector needs dot (.) [OK]

Hint: Class selectors always start with a dot (.) [OK]

Common Mistakes:

• Forgetting the dot before class name
• Confusing element selectors with class selectors
• Assuming uppercase class names are required

5. You want to style all buttons with class primary to have a blue background and white text, but only when hovered. Which CSS code correctly uses class selectors and pseudo-classes?

hard

A. .primary:hover { background-color: blue; color: white; }

B. #primary:hover { background-color: blue; color: white; }

C. button.primary { background-color: blue; color: white; }

D. .primary { background-color: blue; color: white; }

Solution

1. Step 1: Identify correct class selector with hover

   To style elements with class "primary" on hover, use .primary:hover.

2. Step 2: Check other options

   #primary targets an ID, not class. button.primary styles all buttons with class but not on hover. .primary styles all with class but no hover effect.

3. Final Answer:

   .primary:hover { background-color: blue; color: white; } -> Option A

4. Quick Check:

   Class selector + :hover pseudo-class = .primary:hover { background-color: blue; color: white; } [OK]

Hint: Use .class:hover for hover styles on class elements [OK]

Common Mistakes:

• Using # instead of . for class selectors
• Forgetting :hover for hover effect
• Styling without hover when hover is needed