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Font size in CSS - Cheat Sheet & Quick Revision

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Recall & Review
beginner
What CSS property controls the size of text on a webpage?
The font-size property controls how big or small the text appears.
Click to reveal answer
beginner
What unit is recommended for font sizes to support responsive design?
Using relative units like rem or em is recommended because they scale better on different screen sizes.
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intermediate
How does 1rem relate to font size?
1rem equals the font size of the root element (<html>). If the root font size is 16px, then 1rem is 16px.
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intermediate
What happens if you set font size using pixels (px)?
Pixels set a fixed size that does not scale with user settings or screen size, which can hurt accessibility and responsiveness.
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advanced
Why is it important to use semantic HTML with font size styling?
Semantic HTML helps screen readers and browsers understand content structure, so font size changes enhance readability without breaking meaning.
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Which CSS unit is best for scalable font sizes?
Acm
Bpx
Crem
Dpt
What does font-size: 2em; mean?
ATwice the size of the parent element's font size
BTwice the size of the root element's font size
C2 pixels
D2 points
Which property would you use to increase text size in CSS?
Atext-size
Bfont-size
Cfont-weight
Dtext-style
Why avoid using only px for font sizes?
ABecause <code>px</code> does not scale with user settings
BBecause <code>px</code> changes color
CBecause <code>px</code> is slower to load
DBecause <code>px</code> is not supported by browsers
What is the default font size in most browsers if not changed?
A20px
B12px
C10px
D16px
Explain how to set font size in CSS for a paragraph that scales well on different devices.
Think about relative units and why they help with different screen sizes.
You got /4 concepts.
    Describe why accessibility matters when choosing font sizes in web design.
    Consider how different users might need different text sizes.
    You got /5 concepts.

      Practice

      (1/5)
      1. What does the CSS property font-size control on a webpage?
      easy
      A. The color of the text
      B. The background color of the text
      C. The spacing between letters
      D. The size of the text displayed

      Solution

      1. Step 1: Understand the role of font-size

        The font-size property in CSS sets how big or small the text appears on the screen.

      2. Step 2: Compare with other text properties

        Other properties like color or spacing control different aspects, not size.

      3. Final Answer:

        The size of the text displayed -> Option D

      4. Quick Check:

        font-size controls text size [OK]
      Hint: Font size changes text height, not color or spacing [OK]
      Common Mistakes:
      • Confusing font-size with color or spacing properties
      • Thinking font-size changes background color
      • Mixing font-size with letter-spacing
      2. Which of the following is the correct CSS syntax to set the font size to 16 pixels?
      easy
      A. font-size: '16px';
      B. font-size = 16px;
      C. font-size: 16px;
      D. font-size: 16;

      Solution

      1. Step 1: Recall CSS property syntax

        CSS uses a colon (:) to assign values, and units like px must be without quotes.

      2. Step 2: Check each option

        font-size: 16px; uses correct syntax: property, colon, value with unit, and semicolon.

      3. Final Answer:

        font-size: 16px; -> Option C

      4. Quick Check:

        Correct CSS syntax uses colon and units without quotes [OK]
      Hint: Use colon and units without quotes for CSS properties [OK]
      Common Mistakes:
      • Using equal sign instead of colon
      • Putting units inside quotes
      • Omitting units like px
      3. What will be the visual result of this CSS on a paragraph?
      p { font-size: 2rem; }
      medium
      A. The paragraph text will be half the root font size
      B. The paragraph text will be twice the root font size
      C. The paragraph text will be 2 pixels tall
      D. The paragraph text size will not change

      Solution

      1. Step 1: Understand the unit rem

        rem means "root em" and is relative to the root (html) font size.

      2. Step 2: Interpret 2rem

        Setting font-size to 2rem means text will be twice as big as the root font size.

      3. Final Answer:

        The paragraph text will be twice the root font size -> Option B

      4. Quick Check:

        2rem doubles root font size [OK]
      Hint: rem units scale relative to root font size [OK]
      Common Mistakes:
      • Thinking rem is pixels
      • Confusing rem with em
      • Assuming no change in size
      4. Identify the error in this CSS code snippet:
      h1 { font-size: 20; }
      medium
      A. Missing unit after the number
      B. Incorrect property name
      C. Missing semicolon
      D. Font size cannot be set on h1

      Solution

      1. Step 1: Check the font-size value format

        CSS requires a unit like px, em, rem after numeric values for font-size.

      2. Step 2: Identify the missing unit

        The code uses "20" without any unit, which is invalid.

      3. Final Answer:

        Missing unit after the number -> Option A

      4. Quick Check:

        Font size needs units like px or rem [OK]
      Hint: Always add units like px or rem after font-size numbers [OK]
      Common Mistakes:
      • Omitting units like px or rem
      • Assuming numbers alone are valid
      • Confusing semicolon errors
      5. You want to make all paragraph text larger but keep it responsive to user settings. Which CSS rule is best?
      p { font-size: ?; }
      hard
      A. font-size: 1.2rem;
      B. font-size: 18px;
      C. font-size: 120%;
      D. font-size: 1.2em;

      Solution

      1. Step 1: Understand responsiveness and user settings

        To respect user font preferences (e.g., browser font size settings), use units relative to the root element.

      2. Step 2: Compare options for responsiveness

        px is fixed and doesn't scale with user changes. em and % are relative to parent and can compound in nesting. rem is relative to root font size, scaling perfectly with user settings.

      3. Step 3: Choose the best option

        1.2rem increases size by 20% relative to root, ideal for accessibility and responsiveness.

      4. Final Answer:

        font-size: 1.2rem; -> Option A

      5. Quick Check:

        rem units scale with root font size and user settings [OK]
      Hint: Use rem units for scalable font sizes responsive to user preferences [OK]
      Common Mistakes:
      • Using fixed px units ignoring user preferences
      • Using em which can compound unexpectedly
      • Confusing em/% with root-relative rem