CSS Performance Optimization Quiz

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Question 1/15

Which CSS feature, if used incorrectly, can lead to unnecessary repaints and reflows, negatively impacting performance?

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Question 2/15

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

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Question 3/15

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

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Question 4/15

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

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Question 5/15

How does critical CSS enhance the user experience specifically for 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

How does deferring or async loading of CSS affect page performance metrics like FCP (First Contentful Paint)?

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Question 8/15

How can you optimize CSS animations for better performance in modern browsers?

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Question 9/15

What issues can arise if CSS is not effectively minified before deployment?

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Question 10/15

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

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Question 11/15

Which part of the CSSOM (CSS Object Model) might lead to layout thrashing during interactive operations like animations?

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Question 12/15

Which performance issue may arise from incorrect cascading of CSS styles in a large application?

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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

What is the main advantage of using CSS Grid over CSS Flexbox for performance optimization?

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Question 15/15

Which technique allows efficient use of media queries for optimizing CSS performance?

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Your Answers

Question 1/15
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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 2/15
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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 3/15
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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 4/15
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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 5/15
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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 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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How does deferring or async loading of CSS affect page performance metrics like FCP (First Contentful Paint)?

Available answers

By deferring the load of non-critical CSS, the browser can prioritize rendering the viewport content, thus improving metrics such as First Contentful Paint (FCP).
Question 8/15
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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 9/15
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What issues can arise if CSS is not effectively minified before deployment?

Available answers

Not minifying CSS leads to larger file sizes, which in turn means longer download times and slower initial page loads, thus impacting the overall performance and user experience.
Question 10/15
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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 11/15
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Which part of the CSSOM (CSS Object Model) might lead to layout thrashing during interactive operations like animations?

Available answers

The style resolution during animations can cause layout thrashing if style reads and writes are not batched correlatively, as frequent recalculations can lead to dropped frames and jank.
Question 12/15
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Which performance issue may arise from incorrect cascading of CSS styles in a large application?

Available answers

Incorrect cascading in CSS can lead to excessive specificity, meaning changes to styles might require significant recalculation and reapplication of styles impacting performance, especially in large applications.
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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What is the main advantage of using CSS Grid over CSS Flexbox for performance optimization?

Available answers

CSS Grid allows defining both rows and columns in a layout, often reducing the number of complex nesting and code needed, which can lessen layout recalculations compared to Flexbox used in certain scenarios.
Question 15/15
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Which technique allows efficient use of media queries for optimizing CSS performance?

Available answers

A mobile-first approach involves applying base styles that are progressively enhanced using media queries as screen size or device capabilities increase, ensuring only necessary styles are applied initially, reducing overhead.