Prepare for CSS interviews with this extensive list of 60+ questions and answers, a list of CSS interview questions and divided the questions into four sections: basic CSS interview questions, intermediate CSS interview questions, advanced CSS interview questions, and frequently asked CSS interview questions. This list would be helpful for both experienced professionals and freshers. Let us start with this CSS interview questions guide.
Let us begin with the basic CSS interview questions!
CSS frameworks are libraries that make web page styling easier. Some of them are Foundation, Bootstrap, Gumby, Ukit, Semantic UI, etc.
A universal selector is a selector that matches any element type's name instead of selecting elements of a particular type.
Example:
<style>
* {
color: blue;
font-size: 10px;
}
</style>
The ruleset is used for the identification of selectors, which can be attached with other selectors. The two parts of a ruleset are:
The CSS box model defines the layout and design of CSS elements. The elements are content (like text and images, padding (the area around content), border (the area around padding), and margin (the area around the border).
The main difference between CSS3 and CSS2 is that CSS divides different sections into modules and supports many browsers. It also contains new General Sibling Combinators responsible for matching similar elements.
There are three ways of integrating CSS into HTML: using style tags in the head section, using inline-styling, writing CSS in a separate file, and linking into the HTML page by the link tag.
With CSS, different documents can be controlled using a single site, styles can be grouped in complex situations using selectors and grouping methods, and multiple HTML elements can have classes.
RGB represents colors in CSS. The three streams are namely Red, Green, and Blue. The intensity of colors is represented using numbers 0 to 256. This allows CSS to have a spectrum of visible colors.
CSS was developed to define the visual appearances of websites. It allows developers to separate the structure and content of a website that was not possible before.
Ans. Class is a way of using HTML elements for styling. They are not unique and have multiple elements. Whereas ID is unique and it can be assigned to a single element.
In the next section, let us learn some intermediate level CSS interview questions!
This is one of the most frequently asked CSS interview questions. Z-index is used to specify the stack order of elements that overlap each other. Its default value is zero and can take both negative and positive values. A higher z-index value is stacked above the lower index element. It takes the following values- auto, number, initial, and inherit.
With CSS sprites, loading multiple images is not an issue.
Multiple elements can be targeted by separating with a comma:
h2, h3 {color: red;}
The different media types allowed by CSS are:
The background-repeat property is used to control the image. Example:
h3 {
background-repeat: none;
}
The background-attachment property is used to set whether the background image is fixed or it scrolls with the rest of the page. Example for a fixed background-image:
body {
background-image: url(‘url_of_image’);
background-repeat: no-repeat;
background-attachment: fixed;
}
The font-related attributes are Font- style, variant, weight, family, size, etc.
In CSS, contextual selectors allow developers to specify styles of different parts of the document. Styles can be assigned directly to specific HTML tags or create independent classes and assign tags to them.
Responsive Design is a web page creation approach that uses flexible images, flexible layouts, and CSS media queries. This design approach aims to build web pages that detect the orientation and screen size of the visitors so that the layout can be changed accordingly.
In CSS, the styling commands are written in value and property fashion. CSS includes a system terminator- semicolon. The entire style is wrapped in curly braces and attached to the selector. This creates a style sheet that can be applied to an HTML page.
Universal Selector, Element type Selector, ID selector, Class selector, Descendant combinatory, Child Combinator, General Sibling Combinator, Adjacent sibling combinator, and Attribute selector.
CSS preprocessor is a tool used to enhance the basic functionality and let us use the complex logical syntax such as variables, functions, mixins, and code nesting within vanilla CSS scripts themselves.
People use SASS, LESS, and Stylus in order to extend the basic functionality of vanilla CSS.
VH and VW are CSS units used to measure viewport height and viewport width respectively in percentage form in the responsive design techniques. E.g. If the height of the browser is 1000px, then VH is 1/100 of the height of the viewport that is 1000px*(1/100) = 10px, which is the height of the browser. The same applies to VW (viewport width).
Yes, it is the most crucial thing or the most important trial to do when you design a webpage for the first time and make changes to it. Testing your website periodically in different browsers will help you make every webpage compatible with it as browsers have been going through many updates.
Pseudo-classes are the type of pseudo-elements that don’t exist in a normal document tree. It allows selecting the regular elements under certain conditions especially when we try to hover over the link; the anchor tags are :link, :visited, :hover, :active, :focus
In this example, the color will be red on the anchor tag when it’s hovered.
/* mouse over link */
a:hover {
color: #FFOOFF;
}
There are mainly four different units in the CSS that are px, em, pt, and percentage (%).
No, mMargin-top or margin-bottom does not have an effect on the inline elements.
The font-family property is used for changing the font face that is applied to the element in the DOM.
Initially, there is a filtration of elements in the DOM via browsers with respect to key selectors that are traversed until we get parents' elements to determine the matches. Then the browser works on finding all the span elements present in the DOM and traverses them to parent elements to check whether they are matched to paragraph p elements. At last, when the browser finds all matches as parents, the matching process will be stopped and there will be black color applied to the content.
Border-box consists of properties such as content, padding, and the border with respect to height and width. However, Content-box is a default value property used for the box-sizing as well as it helps to add border and padding to give proper height and width to the box without having a border and padding properties.
Opacity is the measure of content transparency. It is measured in the range from 0 to 1. Value 1 means the content is completely opaque. It is not supportable in the internet browser. Also, the 60% of opacity is applicable in the div section where we need to apply the filter property (polyfill) to make it completely opaque.
Cascading is defined as the process of style declaration and its weight that will help the browser in selecting the styling rules with respect to time.
DOM reflow occurs when you insert, move, update, remove, and animate the elements in the DOM as well as when you modify content on the page and change style.
Content-box, Padding-box and Border-box
A div inside another div A is center aligned with the help of aligning div property to content via HTML script and CSS to the element in the DOM.
The CSS grid system is a type of powerful layout of 2 dimensional systems with respect to columns and rows.
display: none, visibility: hidden, position: absolute
The: root selector pseudo-class refers to the CSS selector level 3. It helps to target the highest-level parent element present in the DOM.
Accessibility is to make the system accessible in such a manner that the website should have the text-to-speech capability, for people with physical disabilities, designed with the help of software or hardware combinations.
keyword “initial” is used to restore the default value of a property.
Calc can be used to specify the result of the mathematical operation of two or more elements. For example to specify the width elements by the addition of two or more elements, we can write as
.foo {
Width: calc(100px+50px)
}
CSS Custom properties variables are defined for CSS variables as well as cascading variables with specific values that can be reused.
Box-sizing: border-box is used to provide the inner dimension for the elements in the document by providing padding and border with respect to the height and width of the content.
The style “!important” in the CSS has the highest precedence. Also, the cascaded property will be overridden with it.
Progressive rendering is the process of improving the performance of a webpage with respect to loading time in order to display the content speedily. The use of loading the lazy loading of the image with the help of Intersection Observer API via viewport.
No. The CSS file will be downloaded via browser in order to appear on the HTML page.
@support tag in the CSS is used to scan and determine whether the browser supports a certain feature or not.
Absolute positioning is used to place the element which is then removed from the HTML document from the normal workflow without creating any space for the element in the HTML page layout. The element can be positioned respectively to the closest positioned ancestor; otherwise, if the ancestor is not found, the element is placed with respect to the initial container box. The values provided to the top, right, left and bottom determine the final position of the element.
Overflow: the hidden property is used to specify the content’s clipping. We need to add scrollbars to the content area at the time of specified container size exceeding the content limit where the content gets enclosed. This makes the content invisible via clipping; also the overflow value will be hidden.
Here are some advanced CSS interview questions!
Translate is a CSS transform value. On changing opacity or transform, browser reflow or repaint is not triggered. Transform requires the browser to create a GPU layer for elements but using the CPU changes absolutes positioning properties. Translate () is more efficient and results in shorter paint times. On using translate (), element occupies original space, unlike in changing absolute positioning.
The positioning property specifies the positioning method type. The five different position values are fixed, static, absolute, sticky, and relative. The elements are positioned using top, left, right, and bottom properties. These properties need to be set first, and they work depending on position value.
A mixin is similar to a function block of code returning a single value—mixin output lines of Sass code that directly compiles into CSS styles. At the same time, the function returns a value that becomes the value for a CSS property or something that can be passed to another mixin.
Identify and control 'content areas' of the website. A website generally has a footer, header, sidebar, navbar, and main content area. Most of the work is done by controlling the content area. So, conquer print media without changing the website's integrity by using page breaks, creating a stylesheet for print, size your page for print, and avoid unnecessary HTML tables.
When a browser displays a document, it combines style information and document content. The document is processed in two stages:
ID Selector:
<style>
{
text-align: right;
color: blue;
}
</style>
CSS class Selector:
<style>
.right {
text-align: right;
color: blue;
}
</style>
The float property of CSS positions an image to the right or left as needed, including text wrapping around it. All properties of elements used before it remain unchanged.
Pseudo-elements provide special effects to some selectors. CSS finds use in applying styles in HTML markups. If additional markup or style is not feasible for a document, the pseudo-elements help by allowing extra markup without interfering with the original document.
Logical tags mainly focus on content and are older as compared to physical ones. Logical ones do not find much usage in presentation and terms of aesthetics. At the same time, physical ones find application in presentation.
The four types of media properties are print, speech, and screen. Example of using print-media type:
@media print {
h2 {
background-color: blue;
}
}
In this last section, we look at the most frequently asked CSS interview questions!
CSS3 is divided into modules and is supported by almost every browser. Many graphics-related characteristics are introduced in CSS3 like box-shadow, Border-radius, and flexbox. A user can create precise multiple background images using properties like background-position, background-repeat, and background-image styles.
With a CSS selector, we can choose the content we want to style to bridge between HTML files and style sheets. CSS selector syntax is "select" HTML elements created on their class, id, type, etc.
A group of images placed into one image is a CSS image script. It can reduce load time and project multiple images into a single web page.
CSS specificity is a rank or score that decides style declaration to be used to an element. ID selectors have high specificity, while universal selector * has low specificity. The four CSS categories that authorize the selector's specificity level are IDs, inline style, elements/pseudo-elements, and classes and attributes.
A property of CSS that allows displaying smooth transformation between two or more specified colors. The types of gradients are linear and radial.
The properties of flexbox are flex-direction, wrap, flow, content, and align-items, and content.
The CSS Box model is a box binding HTML element that includes padding, border, margin, and the actual content. With the box model, we get the authority to add a border all around elements and define space between elements.
The four-position states in CSS are relative, static, absolute, and fixed. The default position state is static.
The main difference is that relative is used for the same tag in CSS. If we write right:20 px, then padding shifts 20 px in the right. Whereas absolute is relative to the non-static parent, i.e., if we write right:20 px, the result will be 20 px far from the right edge of the parent element.
Both class and ID are used in HTML to assign a value from CSS. The ID is used as an element, whereas the class is used as a block.
With this, we conclude our CSS interview questions article, and there is a high probability that your interviewer asks you these questions.
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