CSS: Basic Syntax and Selectors

CSS (Cascading Style Sheets) is a stylesheet language used for describing the look and formatting of HTML elements. It allows you to separate the presentation and layout aspects of a website from its content. To understand the basic syntax and selectors in CSS, let's break them down into their main components.

1. Basic Syntax:

A CSS rule consists of two main parts: a selector and a declaration block. The selector targets specific HTML elements, while the declaration block contains one or more declarations that apply styling to the selected elements. Each declaration includes a CSS property and its value, separated by a colon. Multiple declarations within a block are separated by semicolons.

Here's the general structure of a CSS rule:

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selector {
  property: value;
  property: value;
}

For example, to style all paragraphs with a red font color and 16px font size, the CSS rule would look like this:

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p {
  color: red;
  font-size: 16px;
}

2. Selectors:

Selectors are used to target specific HTML elements on a web page. There are various types of selectors in CSS:

a. Element (Type) Selector: Targets all elements of a specific type (e.g., p, h1, div).

Example:

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h1 {
  font-size: 24px;
}

b. Class Selector: Targets elements with a specific class attribute. In CSS, class selectors are prefixed with a period (.).

Example: HTML:

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<p class="highlight">Highlighted text</p>

CSS:

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.highlight {
  background-color: yellow;
}

c. ID Selector: Targets an element with a specific ID attribute. In CSS, ID selectors are prefixed with a hash (#). IDs should be unique within a page.

Example: HTML:

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<div id="header">Header content</div>

CSS:

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#header {
  height: 100px;
  background-color: blue;
}

d. Attribute Selector: Targets elements with a specific attribute or attribute value.

Example: HTML:

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<input type="text" placeholder="Username">

CSS:

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input[type="text"] {
  border: 1px solid gray;
}

e. Pseudo-class Selector: Targets elements based on their state or position in the document. Pseudo-classes are prefixed with a colon (:).

Example:

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a:hover {
  color: red;
}

p:first-child {
  font-weight: bold;
}

f. Pseudo-element Selector: Targets specific parts of an element (e.g., the first letter or first line of a paragraph). Pseudo-elements are prefixed with two colons (::).

Example:

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p::first-letter {
  font-size: 24px;
  font-weight: bold;
}

g. Combinators: These allow you to target elements based on their relationships with other elements, such as descendant, child, adjacent sibling, or general sibling.

Example:

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/* Descendant combinator (space) */
nav li {
  display: inline;
}

/* Child combinator (>) */
ul > li {
  list-style-type: none;
}

/* Adjacent sibling combinator (+) */
h1 + p {
  margin-top: 10px;
}

/* General sibling combinator (~) */
h1 ~ p {
  font-size: 14px;
}

By understanding the basic syntax and different types of selectors in CSS, you can effectively target and style HTML elements to create visually appealing web designs.