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CSS Performance Optimization Quiz

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Question 1/15

Which practice can help avoid text layout shifts during page loading?

Select your answer

Load all fonts asynchronously without a fallback.

Use the

font-display: optional;

property to control font loading behavior.

Preload all fonts using JavaScript before displaying content.

Force all text to visibility: hidden until fonts are loaded.

Question 2/15

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

Select your answer

It's required for all new CSS standards.

Ensures the CSS is compatible across all browsers by default.

Directly keeps the CSSOM size smaller.

Keeps the code cleaner and reduces the risk of applying unsupported CSS, improving performance stability.

Question 3/15

Why is it important to specify the size for images used in CSS backgrounds for performance optimization?

Select your answer

It prevents the images from loading at runtime.

It ensures the image doesn’t stretch unnecessarily, saving layout calculations.

It reduces the image file size automatically.

It avoids the need for image compression.

Question 4/15

Why should you avoid using

selectors in performance-critical CSS?

Select your answer

They target every DOM element, causing all elements to be reconsidered during style recalculations.

They only work in older browsers.

Browsers have slower support for these selectors.

They increase CSS specificity unnecessarily.

Question 5/15

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

Select your answer

Increased parsing time due to redundancy.

Validation errors in the HTML.

Increased specificity leading to potentially higher recalculation times when styles change dynamically.

Cross-browser rendering issues.

Question 6/15

How does critical CSS enhance the user experience specifically for performance?

Select your answer

It organizes the CSS into logical pieces reducing parse time.

It inlines the styles needed for the initial viewport, decreasing time-to-first-render and initial page load times.

It forces browsers to render pages without any styling initially.

It ensures all CSS is cached for subsequent page loads, improving speed.

Question 7/15

Which CSS technique might be used to ensure layout transition animations are smooth with minimal repaint and reflow?

Select your answer

Avoiding transitions by using instant changes.

Employing properties like

transform

and

opacity

, which can be handled by the GPU.

Using CSS animations on properties like width and height.

Utilizing JavaScript timers to precisely control animations.

Question 8/15

What is a potential downside of using CSS custom properties ( var(--my-variable-name) ) on very high-dynamic elements for performance?

Select your answer

They are not yet supported in all browsers.

They can only be used for colors.

They do not work with JavaScript CSSOM.

The dynamic nature requires recalculations that could lead to performance bottlenecks if used excessively.

Question 9/15

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

Select your answer

More efficient debugging using source maps.

Incorrect specificity calculations.

Increased parse errors in specific browsers.

Slower page loads due to increased file size.

Question 10/15

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

Select your answer

Selector matching in the computed view.

Parsing of raw CSS files.

Style resolution during animations.

Recalculation of specificity during changes.

Question 11/15

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

Select your answer

Combine all CSS files into one large file regardless of usage.

Use a tool like PurgeCSS to remove unused styles.

Manually remove all styles that seem unnecessary.

Rely on CSS minification alone.

Question 12/15

Which of the following CSS rules will most likely lead to a performance bottleneck due to inefficient selector usage?

Select your answer

div + p :nth-child(3)

div > p

.container *[data-attr]

.banner > .title

Question 13/15

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

Select your answer

Always use JavaScript to manage animations.

Reduce the use of CSS keyframes in animations.

Use hardware-accelerated properties such as

transform

and

opacity

Avoid using animations on any element.

Question 14/15

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

Select your answer

@font-face

flex

float

position: absolute

Question 15/15

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

Select your answer

They utilize server-side caching automatically.

They enable client-side preprocessing.

They help organize and manage styles, reducing redundancy and file size before delivery.

They inherently make styles render faster.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which practice can help avoid text layout shifts during page loading?

Available answers

Load all fonts asynchronously without a fallback.

Use the <pre><code>font-display: optional;</code></pre> property to control font loading behavior.

Preload all fonts using JavaScript before displaying content.

Force all text to visibility: hidden until fonts are loaded.

Using

font-display: optional;

allows the browser to swap fonts without waiting, preventing layout shifts or flashes of invisible text while prioritizing initial content display.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

It's required for all new CSS standards.

Ensures the CSS is compatible across all browsers by default.

Directly keeps the CSSOM size smaller.

Keeps the code cleaner and reduces the risk of applying unsupported CSS, improving performance stability.

@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 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why is it important to specify the size for images used in CSS backgrounds for performance optimization?

Available answers

It prevents the images from loading at runtime.

It ensures the image doesn’t stretch unnecessarily, saving layout calculations.

It reduces the image file size automatically.

It avoids the need for image compression.

Specifying image sizes allows the page layout to allocate space for images before they load, preventing reflows and unnecessary layout recalculations.

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why should you avoid using <pre><code>*</code></pre> selectors in performance-critical CSS?

Available answers

They target every DOM element, causing all elements to be reconsidered during style recalculations.

They only work in older browsers.

Browsers have slower support for these selectors.

They increase CSS specificity unnecessarily.

Using the universal selector

forces the browser to consider all DOM elements, leading to slower style recalculations, hence decreasing performance.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

Increased parsing time due to redundancy.

Validation errors in the HTML.

Increased specificity leading to potentially higher recalculation times when styles change dynamically.

Cross-browser rendering issues.

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 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does critical CSS enhance the user experience specifically for performance?

Available answers

It organizes the CSS into logical pieces reducing parse time.

It inlines the styles needed for the initial viewport, decreasing time-to-first-render and initial page load times.

It forces browsers to render pages without any styling initially.

It ensures all CSS is cached for subsequent page loads, improving speed.

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 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which CSS technique might be used to ensure layout transition animations are smooth with minimal repaint and reflow?

Available answers

Avoiding transitions by using instant changes.

Employing properties like <pre><code>transform</code></pre> and <pre><code>opacity</code></pre>, which can be handled by the GPU.

Using CSS animations on properties like width and height.

Utilizing JavaScript timers to precisely control animations.

Using

transform

and

opacity

properties ensures that animations are offloaded to the GPU, minimizing the need for CPU-intensive style recalculations, repaints, and reflows.

Question 8/15

😊 Your 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

They are not yet supported in all browsers.

They can only be used for colors.

They do not work with JavaScript CSSOM.

The dynamic nature requires recalculations that could lead to performance bottlenecks if used excessively.

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 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

More efficient debugging using source maps.

Incorrect specificity calculations.

Increased parse errors in specific browsers.

Slower page loads due to increased file size.

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

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

Selector matching in the computed view.

Parsing of raw CSS files.

Style resolution during animations.

Recalculation of specificity during changes.

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 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

Combine all CSS files into one large file regardless of usage.

Use a tool like PurgeCSS to remove unused styles.

Manually remove all styles that seem unnecessary.

Rely on CSS minification alone.

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.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following CSS rules will most likely lead to a performance bottleneck due to inefficient selector usage?

Available answers

<pre><code>div + p :nth-child(3)</code></pre>

<pre><code>.container *[data-attr]</code></pre>

<pre><code>.banner > .title</code></pre>

The selector

div + p :nth-child(3)

uses a pseudo-class (:nth-child) and a sibling selector (+), which can be computationally expensive because the browser may need to examine a significant portion of the DOM to find matching elements.

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

Always use JavaScript to manage animations.

Reduce the use of CSS keyframes in animations.

Use hardware-accelerated properties such as <pre><code>transform</code></pre> and <pre><code>opacity</code></pre>.

Avoid using animations on any element.

Using properties like

transform

and

opacity

leverages GPU acceleration, improving animation performance compared to other properties that may trigger reflows or repaints.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

<pre><code>float</code></pre>

<pre><code>position: absolute</code></pre>

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 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

They utilize server-side caching automatically.

They enable client-side preprocessing.

They help organize and manage styles, reducing redundancy and file size before delivery.

They inherently make styles render faster.

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.