Specificity rules in CSS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all paragraphs with class 'highlight'.

CSS

p[1]highlight { color: red; }

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

A.

B#

C:

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '#' which selects by ID instead of class.

Using ':' which is for pseudo-classes.

Using '*' which selects all elements.

The dot . is used to select elements by their class name in CSS.

2fill in blank

medium

Complete the code to select an element with ID 'main'.

CSS

[1]main { background-color: yellow; }

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

A#

B:

C.

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' which selects by class instead of ID.

Using ':' which is for pseudo-classes.

Using '*' which selects all elements.

The hash # is used to select elements by their ID in CSS.

3fill in blank

hard

Fix the error in the selector to increase specificity by selecting a button inside a div with class 'container'.

CSS

div[1]container button { font-weight: bold; }

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

A#

B.

C:

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '#' which selects by ID, not class.

Using ':' which is for pseudo-classes.

Using '>' which selects direct children only.

To select elements by class, use a dot .. Here, div.container button selects buttons inside divs with class 'container'.

4fill in blank

hard

Fill both blanks to select all list items inside an unordered list with class 'menu'.

CSS

ul[1]menu [2] { color: blue; }

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

A.

B>

Cli

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using '#' instead of '.' for class selection.

Using '>' which selects only direct children, not all descendants.

Omitting the 'li' element selector.

The selector ul.menu li selects all li elements inside a ul with class 'menu'.

5fill in blank

hard

Fill all three blanks to create a selector that selects all paragraphs with class 'text' inside a section with ID 'content'.

CSS

section[1]content [2].[3] { font-size: 1.2rem; }

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

A#

Bp

Ctext

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' instead of '#' for ID selection.

Omitting the element name 'p'.

Not using a dot before the class name 'text'.

The selector section#content p.text selects all p elements with class 'text' inside the section with ID 'content'.

Practice

1. Which CSS selector has the highest specificity?

easy

A. An ID selector like #header

B. A class selector like .menu

C. An element selector like div

D. A universal selector like *

Solution

1. Step 1: Understand selector types and specificity

   ID selectors have the highest specificity, followed by class selectors, then element selectors.

2. Step 2: Compare given selectors

   #header is an ID selector, which beats class .menu and element div selectors.

3. Final Answer:

   An ID selector like #header -> Option A

4. Quick Check:

   ID selector > class selector > element selector [OK]

Hint: ID selectors always outrank classes and elements [OK]

Common Mistakes:

• Thinking class selectors have higher specificity than IDs
• Confusing element selectors with class selectors
• Ignoring the universal selector has lowest specificity

2. Which of the following CSS selectors is written with correct syntax?

easy

A. .container > #main .item

B. #main .container > .item#

C. .container #main .item#

D. #main > .container .item#

Solution

1. Step 1: Check each selector for valid CSS syntax

   Valid selectors use IDs with # before the name, classes with ., and combinators like > properly placed.

2. Step 2: Identify invalid parts

   Options A, B, and D end with # which is invalid syntax. .container > #main .item is correctly formed.

3. Final Answer:

   .container > #main .item -> Option A

4. Quick Check:

   Valid CSS selector syntax = .container > #main .item [OK]

Hint: IDs start with # and never end with # [OK]

Common Mistakes:

• Placing # at the end of selectors
• Misusing combinators like >
• Mixing class and ID syntax incorrectly

3. Given the CSS rules below, which color will the <p> element inside <div id="content"> have?

p { color: blue; }
.content p { color: green; }
#content p { color: red; }

medium

A. Blue

B. Red

C. Black (default)

D. Green

Solution

1. Step 1: Calculate specificity of each rule

   p is element selector (lowest), .content p has a class and element, and #content p has an ID and element. ID selector has highest specificity.

2. Step 2: Determine which rule applies

   The #content p rule overrides others because ID selectors beat class and element selectors.

3. Final Answer:

   Red -> Option B

4. Quick Check:

   ID selector rule wins = Red color [OK]

Hint: ID selectors override class and element selectors [OK]

Common Mistakes:

• Choosing class selector color over ID selector
• Ignoring specificity order
• Assuming last rule always wins regardless of specificity

4. Why does the following CSS not apply the red color to the <h1> element?

h1 { color: blue; }
#title { color: red; }
.title { color: green; }

HTML:

<h1 class="title" id="header">Hello</h1>

medium

A. Because element selectors have higher specificity than ID selectors

B. Because class selectors always override ID selectors

C. Because the ID selector #title does not match the element's ID

D. Because the CSS syntax is incorrect

Solution

1. Step 1: Match selectors to HTML element

   The element has id="header" and class="title". The selector #title targets an element with ID "title", which does not match.

2. Step 2: Understand why red color is not applied

   Since #title does not match, its rule is ignored. The class selector .title applies green, which overrides the element selector blue.

3. Final Answer:

   Because the ID selector #title does not match the element's ID -> Option C

4. Quick Check:

   ID selector must match element's ID exactly [OK]

Hint: ID selectors must match element's actual ID attribute [OK]

Common Mistakes:

• Assuming class overrides ID selectors
• Confusing ID and class selectors
• Ignoring selector matching rules

5. You have these CSS rules:

.btn { color: black; }
button { color: blue; }
#submit.btn { color: green; }

And this HTML:

<button id="submit" class="btn">Send</button>

What color will the button text be and why?

hard

A. Black, because the first rule always wins

B. Blue, because element selectors override class selectors

C. Black, because class selectors override element selectors

D. Green, because the combined ID and class selector has highest specificity

Solution

1. Step 1: Calculate specificity of each rule

   .btn is class selector (specificity 0,1,0), button is element selector (0,0,1), and #submit.btn combines ID and class (1,1,0), highest specificity.

2. Step 2: Determine which rule applies

   The #submit.btn selector wins because it has the highest specificity, so the color is green.

3. Final Answer:

   Green, because the combined ID and class selector has highest specificity -> Option D

4. Quick Check:

   ID + class selector beats class or element alone [OK]

Hint: Combine ID and class selectors for highest specificity [OK]

Common Mistakes:

• Ignoring combined selector specificity
• Thinking element selector beats class selector
• Assuming first rule always applies