CSS Performance Optimization Quiz
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Question 1/15
Which of these events would likely be most impacted by poor CSS performance?
Select your answer
Question 2/15
How does removing unused CSS media queries contribute to performance improvement in web applications?
Select your answer
Question 3/15
What optimization benefit does using
font-display: swap;
provide for web fonts in CSS?
Select your answer
Question 4/15
How does critical CSS enhance the user experience specifically for performance?
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Question 5/15
Which CSS feature, if used incorrectly, can lead to unnecessary repaints and reflows, negatively impacting performance?
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Question 6/15
What is a potential downside of using CSS custom properties (
var(--my-variable-name)
) on very high-dynamic elements for performance?
Select your answer
Question 7/15
Which CSS property commonly causes reflow and should be used with caution for better performance?
Select your answer
Question 8/15
Which of the following scenarios can result in a repaint of the document in browser rendering?
Select your answer
Question 9/15
Why should you avoid using
*
selectors in performance-critical CSS?
Select your answer
Question 10/15
How does using CSS pre-processing tools like SASS or LESS improve CSS performance?
Select your answer
Question 11/15
Why is it advisable to use only
@supports
rules for checking variable CSS features?
Select your answer
Question 12/15
What technique prevents layout recalculations when adding a large number of CSS-modified elements to the DOM?
Select your answer
Question 13/15
What is a key downside of placing too much CSS inline in HTML for performance purposes?
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Question 14/15
How can you optimize CSS animations for better performance in modern browsers?
Select your answer
Question 15/15
Which strategy is recommended for minimizing unused CSS to improve performance?
Select your answer
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Your Answers
Question 1/15
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answer was correct
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answer was incorrect
Which of these events would likely be most impacted by poor CSS performance?
Available answers
Poorly optimized CSS can severely impact scroll performance as the browser might need to recalculate styles or layouts, leading to janky or sluggish scrolling behavior.
Question 2/15
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answer was correct
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answer was incorrect
How does removing unused CSS media queries contribute to performance improvement in web applications?
Available answers
Unused CSS media queries increase the file size and complexity without contributing to functional styling, meaning removing them leads to a smaller CSS footprint and faster parsing.
Question 3/15
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answer was correct
🙁 Your
answer was incorrect
What optimization benefit does using
font-display: swap;
provide for web fonts in CSS?
Available answers
The
font-display: swap;
property ensures text is displayed immediately using a fallback font until the custom font can be loaded, preventing invisible text (flash of invisible text -- FOIT).
Question 4/15
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answer was correct
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answer was incorrect
How does critical CSS enhance the user experience specifically for performance?
Available answers
Critical CSS involves inlining the necessary CSS for the content above the fold into the HTML to ensure it renders immediately, without waiting for external resources to load, improving user-perceived load times.
Question 5/15
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answer was correct
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answer was incorrect
Which CSS feature, if used incorrectly, can lead to unnecessary repaints and reflows, negatively impacting performance?
Available answers
When
position: absolute
is used incorrectly or excessively, it can increase the complexity of calculating the element's position, potentially leading to costly reflows.
Question 6/15
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answer was correct
🙁 Your
answer was incorrect
What is a potential downside of using CSS custom properties (
var(--my-variable-name)
) on very high-dynamic elements for performance?
Available answers
CSS custom properties are resolved at runtime, meaning changes to them can cause recalculation that, if not managed carefully, can impact performance when applied to many dynamic elements.
Question 7/15
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answer was correct
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answer was incorrect
Which CSS property commonly causes reflow and should be used with caution for better performance?
Available answers
The
width
property often causes reflow because changing the width can affect the layout of the document, meaning other elements may have to be repositioned.
Question 8/15
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answer was correct
🙁 Your
answer was incorrect
Which of the following scenarios can result in a repaint of the document in browser rendering?
Available answers
Changing the text color using the
color
property causes a repaint, as it updates how the pixels of an element are displayed visually, even though it doesn't alter its position or trigger a reflow.
Question 9/15
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answer was correct
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answer was incorrect
Why should you avoid using <pre><code>*</code></pre> selectors in performance-critical CSS?
Available answers
Using the universal selector
*
forces the browser to consider all DOM elements, leading to slower style recalculations, hence decreasing performance.
Question 10/15
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answer was correct
🙁 Your
answer was incorrect
How does using CSS pre-processing tools like SASS or LESS improve CSS performance?
Available answers
CSS preprocessors like SASS and LESS allow for variable use, nesting, and includes that can reduce redundant CSS, leading to smaller file sizes before they reach the client.
Question 11/15
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answer was correct
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answer was incorrect
Why is it advisable to use only
@supports
rules for checking variable CSS features?
Available answers
@supports
rules allow conditional application of CSS depending on browser support for certain features, helping prevent unsupported rules from processing, making CSS more stable and performant.
Question 12/15
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answer was correct
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answer was incorrect
What technique prevents layout recalculations when adding a large number of CSS-modified elements to the DOM?
Available answers
Document fragments allow for elements to be inserted into the DOM in bulk, reducing the number of reflows and layout recalculations needed, thus providing better performance.
Question 13/15
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answer was correct
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answer was incorrect
What is a key downside of placing too much CSS inline in HTML for performance purposes?
Available answers
While inline CSS can improve the initial page load, it prevents styles from being cached across requests, leading to longer load times for subsequent page views.
Question 14/15
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answer was correct
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answer was incorrect
How can you optimize CSS animations for better performance in modern browsers?
Available answers
Using properties like
transform
and opacity
leverages GPU acceleration, improving animation performance compared to other properties that may trigger reflows or repaints.
Question 15/15
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answer was correct
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answer was incorrect
Which strategy is recommended for minimizing unused CSS to improve performance?
Available answers
Tools like PurgeCSS analyze your HTML, JavaScript, and CSS to determine which styles are used and which can be safely removed, reducing the file size and improving load times.