CSS Selectors
CSS selectors are used to "find" (or select) the HTML elements you want to style.
We can divide CSS selectors into five categories:
- Simple selectors (select elements based on name, id, class)
- Combinator selectors (select elements based on a specific relationship between them)
- Pseudo-class selectors (select elements based on a certain state)
- Pseudo-elements selectors (select and style a part of an element)
- Attribute selectors (select elements based on an attribute or attribute value)
The CSS element Selector
The element selector selects HTML elements based on the element name.
EXAMPLE:
Here, all <p> elements on the page will be center-aligned, with a red text color:
p {
text-align: center;
color: red;
}
The CSS id Selector
The id selector uses the id attribute of an HTML element to select a specific element.
The id of an element is unique within a page, so the id selector is used to select one unique element!
To select an element with a specific id, write a hash (#) character, followed by the id of the element.
EXAMPLE:
The CSS rule below will be applied to the HTML element with id="para1":
#para1 {
text-align: center;
color: red;
}
The CSS class Selector
The class selector selects HTML elements with a specific class attribute.
To select elements with a specific class, write a period (.) character, followed by the class name.
EXAMPLE:
In this example all HTML elements with class="center" will be red and center-aligned:
.center {
text-align: center;
color: red;
}
You can also specify that only specific HTML elements should be affected by a class.
EXAMPLE:
In this example only <p> elements with class="center" will be center-aligned:
p.center {
text-align: center;
color: red;
}
HTML elements can also refer to more than one class.
EXAMPLE:
In this example the <p> element will be styled according to class="center" and to class="large":
<p class="center large">This paragraph refers to two classes.</p>
Note: A class name cannot start with a number!
The CSS Universal Selector
The universal selector (*) selects all HTML elements on the page.
EXAMPLE:
The CSS rule below will affect every HTML element on the page:
* {
text-align: center;
color: blue;
}
The CSS Grouping Selector
The grouping selector selects all the HTML elements with the same style definitions.
Look at the following CSS code (the h1, h2, and p elements have the same style definitions):
h1 {
text-align: center;
color: red;
}
h2 {
text-align: center;
color: red;
}
p {
text-align: center;
color: red;
}
It will be better to group the selectors, to minimize the code.
To group selectors, separate each selector with a comma.
EXAMPLE:
In this example we have grouped the selectors from the code above:
h1, h2, p {
text-align: center;
color: red;
}