Fallback values in CSS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a fallback font before the main font.

CSS

body { font-family: [1], Arial, sans-serif; }

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

Abackground

Bcolor

CHelvetica

Dmargin

Attempts:

3 left

💡 Hint

Common Mistakes

Using CSS properties like color or margin instead of a font name.

Leaving the main font blank.

The font-family property lists fonts in order of preference. The first is the main font, followed by fallback fonts.

2fill in blank

medium

Complete the code to provide a fallback background color.

CSS

div { background: [1] linear-gradient(to right, #00ff00); }

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

Ared

Bborder

Cpadding

Dfont-size

Attempts:

3 left

💡 Hint

Common Mistakes

Using CSS properties instead of color values.

Using invalid color names.

The background shorthand property can specify a color fallback before a gradient. The color is used if the gradient is not supported.

3fill in blank

hard

Fix the error in the fallback font list.

CSS

p { font-family: [1], 'Times New Roman', serif; }

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

AArial

Bfont-weight

Ccolor

Dpadding

Attempts:

3 left

💡 Hint

Common Mistakes

Using CSS properties instead of font names.

Leaving the first font blank.

The font-family list should contain font names, not CSS properties.

4fill in blank

hard

Fill both blanks to set a fallback font and a fallback background color.

CSS

h1 { font-family: [1], Verdana, sans-serif; background: [2] linear-gradient(to right, #0000ff); }

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

AGeorgia

Bred

Cblue

Dpadding

Attempts:

3 left

💡 Hint

Common Mistakes

Using CSS properties instead of font names or colors.

Mixing up the order of font and color values.

The first blank is a fallback font name, and the second blank is a fallback background color before the gradient.

5fill in blank

hard

Fill all three blanks to set fallback fonts and a fallback background color with a gradient.

CSS

section { font-family: [1], 'Courier New', monospace; background: [2] linear-gradient(to right, #ff0000, #0000ff) [3]; }

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

ATahoma

Byellow

Cno-repeat

Dpadding

Attempts:

3 left

💡 Hint

Common Mistakes

Using CSS properties instead of font names or colors.

Using invalid background styles.

The first blank is a fallback font, the second is a fallback background color before the gradient, and the third is a background-repeat value.

Practice

1. What is the main purpose of using fallback values in CSS?

easy

A. To make the website load faster

B. To provide backup styles if the main style is not supported

C. To add animations to elements

D. To change the HTML structure dynamically

Solution

1. Step 1: Understand fallback values concept

   Fallback values are used to ensure styles still apply if the preferred style is unsupported by the browser.

2. Step 2: Identify the purpose from options

   Only To provide backup styles if the main style is not supported correctly describes fallback values as backup styles.

3. Final Answer:

   To provide backup styles if the main style is not supported -> Option B

4. Quick Check:

   Fallback values = backup styles [OK]

Hint: Fallback means backup style if main fails [OK]

Common Mistakes:

• Thinking fallback speeds up loading
• Confusing fallback with animations
• Believing fallback changes HTML

2. Which of the following is the correct way to provide fallback fonts in CSS?

easy

A. font-family: sans-serif 'Open Sans';

B. font-family: 'Open Sans';

C. font-family: Arial 'Open Sans';

D. font-family: 'Open Sans', Arial, sans-serif;

Solution

1. Step 1: Recall font-family syntax with fallbacks

   Fallback fonts are listed separated by commas, from preferred to generic.

2. Step 2: Check each option's syntax

   font-family: 'Open Sans', Arial, sans-serif; correctly lists 'Open Sans', then Arial, then generic sans-serif with commas.

3. Final Answer:

   font-family: 'Open Sans', Arial, sans-serif; -> Option D

4. Quick Check:

   Fallback fonts use commas [OK]

Hint: Separate fallback fonts with commas [OK]

Common Mistakes:

• Missing commas between fonts
• Wrong order of fonts
• Using quotes incorrectly

3. What color will the text be if the browser does not support CSS variables in this code?

p { color: var(--main-color, blue); }

medium

A. Blue

B. The color defined by --main-color variable

C. Black (default color)

D. Transparent

Solution

1. Step 1: Understand CSS variable fallback syntax

   The syntax var(--main-color, blue) means use --main-color if supported, else fallback to blue.

2. Step 2: Consider browser support for CSS variables

   If the browser does not support CSS variables, it uses the fallback value blue.

3. Final Answer:

   Blue -> Option A

4. Quick Check:

   Fallback value used when variable unsupported [OK]

Hint: Fallback after comma used if variable unsupported [OK]

Common Mistakes:

• Assuming variable always works
• Choosing default black color
• Confusing fallback with transparency

4. Identify the error in this CSS fallback usage:

div { background-image: url('image.webp', 'image.png'); }

medium

A. Fallback images require multiple url() functions separated by commas

B. Only one URL is allowed inside url() function

C. The URLs should be separated by commas as shown

D. Fallback images are not supported in CSS

Solution

1. Step 1: Understand fallback for background images

   Fallback images are provided by listing multiple url() functions separated by commas.

2. Step 2: Analyze the given code

   The code incorrectly puts two URLs inside one url() function, which is invalid syntax.

3. Step 3: Correct usage

   Correct syntax: background-image: url('image.webp'), url('image.png');

4. Final Answer:

   Fallback images require multiple url() functions separated by commas -> Option A

5. Quick Check:

   Multiple url() with commas for fallback [OK]

Hint: Use separate url() calls for fallback images [OK]

Common Mistakes:

• Putting multiple URLs inside one url()
• Missing commas between url() functions
• Thinking fallback images not supported

5. You want to set a CSS variable --primary-color with a fallback to green if the variable is not defined. Which CSS rule correctly applies this fallback to the text color and background-color?

hard

A. color: var(--primary-color, green); background-color: var(--primary-color);

B. color: var(--primary-color); background-color: green;

C. color: var(--primary-color, green); background-color: var(--primary-color, green);

D. color: green; background-color: var(--primary-color, green);

Solution

1. Step 1: Understand fallback usage for CSS variables

   To ensure fallback works for both color and background-color, each var() must include fallback.

2. Step 2: Analyze each option

   color: var(--primary-color, green); background-color: var(--primary-color, green); uses var(--primary-color, green) for both properties, ensuring fallback if variable undefined.

3. Step 3: Why others are incorrect

   color: var(--primary-color, green); background-color: var(--primary-color); misses fallback for background-color; B misses fallback for color; C sets color fixed to green ignoring variable.

4. Final Answer:

   color: var(--primary-color, green); background-color: var(--primary-color, green); -> Option C

5. Quick Check:

   Fallback in each var() call needed [OK]

Hint: Add fallback inside every var() call [OK]

Common Mistakes:

• Adding fallback only once
• Setting fixed color ignoring variable
• Forgetting fallback for background-color