CSS Performance Optimization Quiz

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Question 1/15

Which of these events would likely be most impacted by poor CSS performance?

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Question 2/15

How does removing unused CSS media queries contribute to performance improvement in web applications?

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Question 3/15

What optimization benefit does using font-display: swap; provide for web fonts in CSS?

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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?

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Question 7/15

Which CSS property commonly causes reflow and should be used with caution for better performance?

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Question 8/15

Which of the following scenarios can result in a repaint of the document in browser rendering?

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Question 9/15

Why should you avoid using
*
selectors in performance-critical CSS?

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Question 10/15

How does using CSS pre-processing tools like SASS or LESS improve CSS performance?

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Question 11/15

Why is it advisable to use only @supports rules for checking variable CSS features?

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Question 12/15

What technique prevents layout recalculations when adding a large number of CSS-modified elements to the DOM?

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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?

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Question 15/15

Which strategy is recommended for minimizing unused CSS to improve performance?

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Your Answers

Question 1/15
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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.