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CSS Performance Optimization Quiz

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Question 1/15

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

Select your answer

It avoids the need for image compression.

It prevents the images from loading at runtime.

It reduces the image file size automatically.

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

Question 2/15

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 do not work with JavaScript CSSOM.

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

They can only be used for colors.

Question 3/15

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

Select your answer

Cross-browser rendering issues.

Increased parsing time due to redundancy.

Validation errors in the HTML.

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

Question 4/15

Why should you avoid using

selectors in performance-critical CSS?

Select your answer

They increase CSS specificity unnecessarily.

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.

Question 5/15

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

Select your answer

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

It's required for all new CSS standards.

Ensures the CSS is compatible across all browsers by default.

Directly keeps the CSSOM size smaller.

Question 6/15

What is a key downside of placing too much CSS inline in HTML for performance purposes?

Select your answer

Higher download time due to more HTTP requests.

It improves first-page rendering at the cost of subsequent loads.

Inline CSS prevents caching of styles across document requests.

Increased specificity can cause issues when overriding styles.

Question 7/15

Which of the following methods would effectively help async load CSS to avoid render-blocking?

Select your answer

Load CSS with JavaScript dynamically.

Inline all CSS into the HTML document.

Use a

<link rel='stylesheet'

element with

media='print'

and change the media type once loaded.

Use a CDN for all CSS assets.

Question 8/15

In which scenario would using CSS variables potentially lead to worse performance?

Select your answer

When CSS variables are used excessively for large-scale theming and calculated often.

When you use them for responsive units like vh, vw.

When CSS variables replace hardcoded colors in several rules.

When they are declared in root and reused in several components.

Question 9/15

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

Select your answer

It disables custom font usage entirely.

It guarantees fonts will load faster than any other setting.

It reduces overall CSS file size.

It ensures fonts are always visible even if there is a delay in loading.

Question 10/15

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

Select your answer

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

Use the

font-display: optional;

property to control font loading behavior.

Load all fonts asynchronously without a fallback.

Preload all fonts using JavaScript before displaying content.

Question 11/15

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

Select your answer

Utilizing JavaScript timers to precisely control animations.

Avoiding transitions by using instant changes.

Using CSS animations on properties like width and height.

Employing properties like

transform

and

opacity

, which can be handled by the GPU.

Question 12/15

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 13/15

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

Select your answer

@font-face

float

position: absolute

flex

Question 14/15

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

Select your answer

It frees up thread processing used for CSSOM generation.

It solidifies CSS specificity rules.

It decreases render time during dynamic viewport changes.

It reduces file size, leading to faster download times and less parsing by the browser.

Question 15/15

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

Select your answer

Slower page loads due to increased file size.

Incorrect specificity calculations.

Increased parse errors in specific browsers.

More efficient debugging using source maps.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 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 avoids the need for image compression.

It prevents the images from loading at runtime.

It reduces the image file size automatically.

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

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

Question 2/15

😊 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 do not work with JavaScript CSSOM.

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

They can only be used for colors.

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 3/15

😊 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

Cross-browser rendering issues.

Increased parsing time due to redundancy.

Validation errors in the HTML.

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

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 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 increase CSS specificity unnecessarily.

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.

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

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

Available answers

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

It's required for all new CSS standards.

Ensures the CSS is compatible across all browsers by default.

Directly keeps the CSSOM size smaller.

@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 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a key downside of placing too much CSS inline in HTML for performance purposes?

Available answers

Higher download time due to more HTTP requests.

It improves first-page rendering at the cost of subsequent loads.

Inline CSS prevents caching of styles across document requests.

Increased specificity can cause issues when overriding styles.

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 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following methods would effectively help async load CSS to avoid render-blocking?

Available answers

Load CSS with JavaScript dynamically.

Inline all CSS into the HTML document.

Use a <pre><code><link rel='stylesheet'</code></pre> element with <pre><code>media='print'</code></pre> and change the media type once loaded.

Use a CDN for all CSS assets.

By using a

<link rel='stylesheet' media='print'

approach, the stylesheet loads without blocking rendering initially. Once loaded, the media type can be changed with JavaScript to apply styles.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

In which scenario would using CSS variables potentially lead to worse performance?

Available answers

When CSS variables are used excessively for large-scale theming and calculated often.

When you use them for responsive units like vh, vw.

When CSS variables replace hardcoded colors in several rules.

When they are declared in root and reused in several components.

When CSS variables are recalculated frequently across many elements or used excessively, they can become a performance bottleneck due to the dynamic nature of how they are recalculated and resolved.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

It disables custom font usage entirely.

It guarantees fonts will load faster than any other setting.

It reduces overall CSS file size.

It ensures fonts are always visible even if there is a delay in loading.

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 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

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

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

Load all fonts asynchronously without a fallback.

Preload all fonts using JavaScript before displaying content.

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 11/15

😊 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

Utilizing JavaScript timers to precisely control animations.

Avoiding transitions by using instant changes.

Using CSS animations on properties like width and height.

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

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 12/15

😊 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 13/15

😊 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 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

It frees up thread processing used for CSSOM generation.

It solidifies CSS specificity rules.

It decreases render time during dynamic viewport changes.

It reduces file size, leading to faster download times and less parsing by the browser.

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 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

Slower page loads due to increased file size.

Incorrect specificity calculations.

Increased parse errors in specific browsers.

More efficient debugging using source maps.

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.