What is CSS ?

CSS, which stands for Cascading Style Sheets, is a fundamental technology used for styling web pages. It works hand in hand with HTML to define the presentation and layout of a web page, including aspects like fonts, colors, spacing, and positioning of elements.

Here's a basic introduction to CSS:


Separation of Concerns: 

CSS allows the separation of content (HTML) from presentation (styling). This separation enhances the maintainability and flexibility of web pages.

Syntax: CSS consists of selectors and declaration blocks. Selectors target HTML elements, and declaration blocks contain the styling properties and their values. Here's a simple example:

 h1 {
     color: blue;
     font-size: 24px;

In this example, h1 is the selector targeting all <h1> elements, and the declaration block contains two styling properties: color and font-size.



 Selectors determine which HTML elements the styles should apply to. They can target elements based on their tag names, classes, IDs, attributes, and relationships with other elements. Some common selectors include:

  • Tag selectors (e.g., h1, p, div)
  • Class selectors (e.g., .classname)
  • ID selectors (e.g., #idname)
  • Attribute selectors (e.g., [type="text"])
  • Descendant selectors (e.g., div p)


Properties and Values:

 CSS properties define the visual aspects of HTML elements, such as colors, fonts, margins, padding, and positioning. Each property can have one or more values assigned to it. For example:

  • color: Sets the text color.
  • font-size: Sets the size of the font.
  • margin: Sets the space outside the element.
  • padding: Sets the space inside the element.
  • border: Sets the border around the element.


Cascade and Specificity: 

CSS follows rules for determining which styles apply when there are conflicting rules. The cascade refers to the order in which styles are applied, with later rules taking precedence over earlier ones. Specificity determines which rule is more specific and therefore applied.



CSS properties can be inherited from parent elements to their children. For example, if you set a font color on the body element, it will be inherited by all its child elements unless overridden.


External, Internal, and Inline Styles:

 CSS can be applied to HTML documents in three ways:

  • External Stylesheets: Linked externally via <link> elements in the HTML <head> section.
  • Internal Stylesheets: Defined within a <style> element in the HTML <head> section.
  • Inline Styles: Applied directly to individual HTML elements using the style attribute.

Understanding CSS is essential for web development, as it enables developers to create visually appealing and responsive web pages. With practice and experimentation, you can leverage CSS to design engaging and user-friendly interfaces for websites and web applications.