CSS syntax and rules - Practice Problems & Coding Challenges

Challenge - 5 Problems

📝 Syntax

intermediate

What is the output of this CSS snippet?

Given the CSS below, what color will the paragraph text be rendered in a browser?

CSS

p { color: blue; color: red; }

A Blue

B Green

C Black (default)

D Red

💡 Hint

Later rules override earlier ones if they have the same specificity.

The last color property in the same rule overrides the previous one. So the paragraph text will be red.

❓ selector

intermediate

Which selector matches only direct children?

Which CSS selector matches only the direct children of a div element?

A div p

B div > p

C div + p

D div ~ p

💡 Hint

Look for the selector that uses the child combinator symbol.

The > symbol selects only direct children. So div > p matches p elements that are immediate children of div.

❓ layout

advanced

What layout will this CSS produce?

Given the CSS below, how will the three boxes be arranged visually?

CSS

.container {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.box {
  width: 100px;
  height: 100px;
  background-color: lightblue;
}

A Boxes arranged vertically in a column with space between

B Boxes arranged horizontally in a row with space between

C Boxes stacked on top of each other with no space

D Boxes arranged randomly with overlapping

💡 Hint

Check the flex-direction property value.

The container uses flexbox with flex-direction: column, so boxes stack vertically. The gap adds space between them.

❓ accessibility

advanced

Which CSS rule improves text accessibility?

Which CSS rule below best improves text readability for users with visual impairments?

A p { color: #999; background-color: #999; }

B p { color: #777; background-color: #eee; }

C p { color: #000; background-color: #fff; }

D p { color: #ccc; background-color: #ddd; }

💡 Hint

Good contrast between text and background helps readability.

Black text on white background (#000 on #fff) provides the highest contrast, making text easier to read.

🧠 Conceptual

expert

What error does this CSS cause?

What error or issue will this CSS cause when applied in a browser?

CSS

div {
  color: blue;
  background-color: yellow;
}

A Syntax error due to missing semicolon after color property

B Background color will not apply but no error

C Both properties apply correctly

D Browser crashes

💡 Hint

Check punctuation between CSS declarations.

Missing semicolon after color: blue causes a syntax error, so the browser ignores the entire rule or stops parsing at that point.

Practice

1. What is the correct order of parts in a CSS rule?

easy

A. Property, value, selector, curly braces

B. Selector, curly braces, property, value

C. Value, property, selector, curly braces

D. Curly braces, selector, property, value

Solution

1. Step 1: Understand CSS rule structure

   A CSS rule starts with a selector that chooses HTML elements to style.

2. Step 2: Identify the syntax order

   The selector is followed by curly braces { }, inside which property: value pairs define styles.

3. Final Answer:

   Selector, curly braces, property, value -> Option B

4. Quick Check:

   CSS rule = Selector + { property: value } [OK]

Hint: Remember: selector first, then braces with property:value inside [OK]

Common Mistakes:

• Putting property before selector
• Omitting curly braces
• Swapping property and value order

2. Which of the following is the correct CSS syntax to set text color to blue?

easy

A. color; blue:

B. color = blue;

C. color-blue;

D. color: blue;

Solution

1. Step 1: Identify property and value separator

   In CSS, properties and values are separated by a colon (:), not an equals sign or other symbols.

2. Step 2: Check correct syntax for color property

   The correct syntax is color: blue; with a colon and semicolon ending the statement.

3. Final Answer:

   color: blue; -> Option D

4. Quick Check:

   Property and value separated by colon : [OK]

Hint: Use colon : between property and value, end with semicolon ; [OK]

Common Mistakes:

• Using equals sign instead of colon
• Missing semicolon at end
• Swapping property and value order

3. What color will the text be in this CSS rule?

p { color: red; color: green; }

medium

A. Green

B. No color applied

C. Both red and green

D. Red

Solution

1. Step 1: Understand CSS property overriding

   When the same property appears multiple times, the last one takes priority.

2. Step 2: Identify which color is last

   The rule sets color: red; first, then color: green; which overrides red.

3. Final Answer:

   Green -> Option A

4. Quick Check:

   Last property value wins in CSS [OK]

Hint: Last property value overrides earlier ones [OK]

Common Mistakes:

• Thinking both colors apply simultaneously
• Choosing the first color instead of last
• Assuming no override happens

4. Find the error in this CSS rule:

h1 { font-size 20px; }

medium

A. Wrong selector name

B. Missing semicolon at end

C. Missing colon between property and value

D. Curly braces are missing

Solution

1. Step 1: Check property-value separator

   The property font-size must be followed by a colon before the value.

2. Step 2: Verify other syntax parts

   Curly braces are present, semicolon is optional if only one property, selector is correct.

3. Final Answer:

   Missing colon between property and value -> Option C

4. Quick Check:

   Property and value must be separated by colon : [OK]

Hint: Always put colon : between property and value [OK]

Common Mistakes:

• Forgetting colon after property
• Confusing semicolon necessity
• Misnaming selectors

5. You want to style all paragraphs inside a section with a blue background and white text. Which CSS rule correctly applies both styles?

hard

A. section p { background-color: blue; color: white; }

B. section, p { background-color: blue; color: white; }

C. section p { background-color = blue; color = white; }

D. section > p { background-color: blue; color: white }

Solution

1. Step 1: Select paragraphs inside section

   The selector section p targets all p elements inside any section.

2. Step 2: Use correct CSS syntax for multiple properties

   Properties must be separated by semicolons and use colon between property and value.

3. Step 3: Check option correctness

   section p { background-color: blue; color: white; } uses correct selector and syntax. section, p { background-color: blue; color: white; } styles both section and p separately, not only p inside section. section p { background-color = blue; color = white; } uses equals sign which is invalid. section > p { background-color: blue; color: white } uses child selector which only selects direct children, not all descendants.

4. Final Answer:

   section p { background-color: blue; color: white; } -> Option A

5. Quick Check:

   Descendant selector + correct syntax = section p { background-color: blue; color: white; } [OK]

Hint: Use descendant selector and colon with semicolon syntax [OK]

Common Mistakes:

• Using commas instead of spaces in selector
• Using equals sign instead of colon
• Confusing child selector > with descendant selector