Universal selector in CSS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the universal selector (*) do in CSS?

The universal selector (*) matches all elements on the page. It applies styles to every HTML element.

beginner

How do you write a CSS rule that sets the font color to blue for all elements using the universal selector?

You write:

* { color: blue; }

This changes the text color of every element to blue.

intermediate

True or False: The universal selector can be combined with other selectors to narrow down styling.

True. For example, div * selects all elements inside div elements.

intermediate

Why should you be careful when using the universal selector (*) in CSS?

Because it applies styles to every element, it can slow down the page and override specific styles unintentionally.

beginner

Give an example of using the universal selector to reset margin and padding for all elements.

Example:

* { margin: 0; padding: 0; }

This removes default spacing from all elements, useful for consistent layout.

What does the CSS universal selector (*) select?

A All elements on the page

B Only <div> elements

C Only elements with a class

D Only elements with an ID

The universal selector (*) matches every element in the HTML document.

Which CSS rule uses the universal selector to remove all default margin and padding?

A #all { margin: 0; padding: 0; }

B div { margin: 0; padding: 0; }

C .all { margin: 0; padding: 0; }

D * { margin: 0; padding: 0; }

The rule with * applies margin and padding reset to all elements.

What is a potential downside of using the universal selector (*) in CSS?

A It can slow down page rendering

B It only styles one element

C It does not work in modern browsers

D It only applies to images

Applying styles to all elements can slow down rendering and cause unintended style overrides.

How can you select all elements inside a <section> using the universal selector?

A section

B * section

C section *

D *

The selector 'section *' selects every element inside all

elements.

Which of these selectors is the universal selector?

A #

B *

C .

D >

The asterisk (*) is the universal selector in CSS.

Explain what the universal selector (*) does in CSS and give a simple example.

Think about how you would style every element on a page at once.

Describe one advantage and one disadvantage of using the universal selector in your CSS.

Consider performance and control over styling.

Practice

1. What does the CSS universal selector * do?

easy

A. Selects elements with a specific class

B. Selects only div elements

C. Selects all elements on the page

D. Selects elements with a specific ID

Solution

1. Step 1: Understand the universal selector symbol

   The * symbol in CSS means "all elements" without exception.

2. Step 2: Apply the selector meaning

   Using * targets every element on the page, regardless of tag, class, or ID.

3. Final Answer:

   Selects all elements on the page -> Option C

4. Quick Check:

   Universal selector = all elements [OK]

Hint: Remember * means every element on the page [OK]

Common Mistakes:

• Thinking * selects only specific tags
• Confusing * with class or ID selectors
• Assuming * targets only visible elements

2. Which of the following is the correct syntax to apply a margin of 0 to all elements using the universal selector?

easy

A. # * { margin: 0; }

B. . * { margin: 0; }

C. all { margin: 0; }

D. * { margin: 0; }

Solution

1. Step 1: Identify the universal selector syntax

   The universal selector is just * without any prefix like dot or hash.

2. Step 2: Check the CSS rule format

   The correct CSS rule to apply margin 0 to all elements is * { margin: 0; }.

3. Final Answer:

   * { margin: 0; } -> Option D

4. Quick Check:

   Universal selector syntax = * { ... } [OK]

Hint: Universal selector is just * without dot or hash [OK]

Common Mistakes:

• Adding dot or hash before *
• Using invalid selector names like 'all'
• Forgetting curly braces

3. Given this CSS code:

* { padding: 10px; }
p { padding: 5px; }

What will be the padding of a paragraph (<p>) element?

medium

A. 10px

B. 5px

C. 15px

D. 0px

Solution

1. Step 1: Understand selector specificity

   The universal selector * applies padding 10px to all elements, but the p selector is more specific.

2. Step 2: Apply CSS specificity rules

   Since p selector is more specific than *, the paragraph's padding will be 5px, overriding the universal selector.

3. Final Answer:

   5px -> Option B

4. Quick Check:

   More specific selector wins = 5px [OK]

Hint: More specific selector overrides * [OK]

Common Mistakes:

• Assuming * always overrides other selectors
• Adding padding values instead of overriding
• Ignoring CSS specificity rules

4. You wrote this CSS:

* { font-size: 16px }

But the browser ignores it and uses default font sizes. What is the likely error?

medium

A. CSS file not linked properly

B. Universal selector cannot set font size

C. Font size must be in quotes

D. Missing semicolon after 16px

Solution

1. Step 1: Check CSS syntax

   The CSS rule * { font-size: 16px } is syntactically valid; a trailing semicolon is optional at the end of a rule.

2. Step 2: Understand common issues

   If valid CSS is ignored by the browser, the stylesheet is likely not linked properly in the HTML with a <link rel="stylesheet" href="..."> tag.

3. Final Answer:

   CSS file not linked properly -> Option A

4. Quick Check:

   No styles applied? Check <link> tag [OK]

Hint: If * styles not applying, verify CSS file link [OK]

Common Mistakes:

• Thinking universal selector can't style fonts
• Using quotes around numeric values
• Ignoring CSS file linking issues

5. You want to reset margin and padding for all elements but keep links (<a>) with no margin and 5px padding. Which CSS achieves this?

hard

A. * { margin: 0; padding: 0; } a { padding: 5px; }

B. a { margin: 10px; padding: 5px; } * { margin: 0; padding: 0; }

C. * { margin: 0; padding: 5px; } a { margin: 0; padding: 0; }

D. * { margin: 0; padding: 0; a { padding: 5px; } }

Solution

1. Step 1: Reset all elements margin and padding

   The universal selector * { margin: 0; padding: 0; } sets margin and padding to zero for all elements.

2. Step 2: Override padding for links

   The selector a { padding: 5px; } specifically sets padding to 5px for all <a> elements, overriding the universal selector.

3. Final Answer:

   * { margin: 0; padding: 0; } a { padding: 5px; } -> Option A

4. Quick Check:

   Specific selector overrides universal [OK]

Hint: Use * first, then override with specific selector [OK]

Common Mistakes:

• Placing universal selector after specific selector
• Nesting selectors incorrectly
• Setting wrong padding values