CSS stands for Cascading Style Sheets. It is a style sheet language introduced by the W3C and is used to control the style and appearance of web documents written in HTML. The idea behind CSS is to manage the color, size, layout, position, and other visual and auditory characteristics of HTML and XHTML documents and their elements.
Advantages
In web development, HTML defines the structure and content of a web page, while CSS orders content is presented to the end user. CSS allows developers to separate the design and styling of a website from its HTML structure. This separation has several advantages:
- CSS saves time by allowing styles to be written once and reused across multiple HTML pages. A single CSS file can define the look for an entire website.
- Pages load faster because using CSS reduces the need to write HTML tag attributes for styling every time. Less code means faster download times.
- The website’s design can be made by modifying the CSS without altering the HTML structure.
- CSS provides more styling capabilities for layout and visual effects than presentational HTML ever could.
- CSS promotes global web standards by encouraging the disapproval of HTML attributes for styling, making web pages more compatible with future browsers.
Essentially, CSS handles the look and feel part of a web page, controlling aspects such as text color, font styles, spacing, column layouts, background images or colors, and various other visual effects. CSS works by associating rules with HTML elements, leading how their content should be displayed. A CSS rule consists of a selector (which targets specific HTML elements) and a declaration block containing one or more declarations. Each declaration includes a property (the aspect to be changed, e.g., color, font-family) and a value (e.g., red, Arial).
The History and Evolution of CSS to CSS3
CSS arose because the original HTML was never planned to contain tags for formatting a document; HTML tags were meant to define the content. The addition of presentational tags like <font> and color attributes in HTML 3.2 led to a “terrible” for web developers, making the development of large websites with consistent styling a long and expensive process.
The CSS developed as early as 1994. The evolution of CSS can be broadly categorized into different levels or versions:
What are the 3 CSS Levels ?
- CSS1 (Level 1): Published as a W3C Recommendation in 1996, CSS1 was the first Cascading Style Sheet specification. It introduced styles for font properties, element color, alignment, tables, margin, border, padding, and positioning. CSS1 properties could be applied to uniquely identified elements or element groups. Although its development has been closed by W3C, most of its features are supported in web browsers, some lesser-used features have small coincidences, especially in older browsers.
- CSS2 (Level 2) and CSS 2.1: CSS Level 2 was developed as a superset of CSS1, adding several new features. The most important additions included layer order (z-index), three types of element positioning (absolute, relative, and fixed), the aural media type, and bidirectional text. CSS Level 2 Revision 1 (CSS 2.1) became the ultimate styling solution for many years and was a W3C Recommendation in 2011. It addressed inconsistencies and errors in the CSS2 specification.
- CSS3 (Level 3): The development of CSS Level 3 (CSS3) began around 2005. Unlike previous versions, CSS3 is modularized. It is described by separate documents called CSS modules, each focusing on a specific area of functionality. Examples of CSS3 modules include Selectors, Media Queries, Text, Backgrounds and Borders, Colors, 2D Transformations, 3D Transformations, Transitions, Animations, and Multi-Columns. These modules are in different stages of development and browser implementation. Some modules, like the Color module, were standardized earlier.
CSS3 aimed to solve presentation-related problems without depend on scripting plugins or extra images. It introduced many exciting new techniques for web designers, such as:
- New CSS Selectors: Allowing for more precise targeting of HTML elements.
- CSS3 Backgrounds and Borders: Including features like background gradients (linear and radial), background-size, background-origin, background-clip, border-radius (rounded corners), and border-shadow (box shadows).
- CSS3 Colors: Introducing new color formats like RGBA and HSLA, providing alpha transparency.
- Web Typography: Improvements including @font-face for embedding custom fonts.
- CSS3 2D and 3D Transformations: Allowing elements to be scaled, rotated, skewed, and translated.
- CSS3 Transitions: Enabling smooth visual effects when an element changes from one state to another.
- CSS3 Animations: Providing the ability to create more complex, keyframe-based animations.
- Flexible Box Layout (Flexbox): A new layout module for creating flexible and responsive one-dimensional layouts.
- CSS Grid Layout: A powerful two-dimensional layout system.
- Media Queries: Allowing websites to adapt their layout and styling to different screen sizes and device capabilities, crucial for responsive web design.
- CSS Custom Properties (Variables): Enabling the definition and reuse of custom values within CSS.
Understanding the module status and browser implementation levels is important for developers to effectively use CSS3. The evolution of CSS, especially with CSS3, has meaningfully improved the capabilities of web development, allowing for richer, more interactive, and responsive user experiences while maintaining the critical separation of content and presentation.