Applying CSS Styles with IDs and Classes in HTML

In web development, it's essential to master the art of styling HTML elements with CSS. This article will delve into the specific techniques and best practices for targeting HTML elements with CSS ID selector and CSS Class selector.

Introduction to CSS Selectors

To style HTML elements with CSS, you must first properly apply a class or an ID to your tag. Here's how:

Using a Class

For styling purposes, you can use a class for your HTML tag. For example, you would reference the class in the following manner:

h1 classtitle1This is a Title/h1

Using an ID

Alternatively, for unique styling or element identification, use an ID:

h1 idtitle2This is a Title/h1

These attributes should be placed within the HTML tags, and the corresponding styles should be defined in the CSS file.

Applying Styles with CSS Selectors

Once you have your classes or IDs set up, you can apply the corresponding styles in the CSS file. Remember, to denote a class, you use a dot (.), and for an ID, you use a hashtag (#).

/* Example of a class selector */.title1 {color: red;}/* Example of an ID selector */#title2 {color: blue;}

Example of Applying CSS to an ID

To apply styles to an ID, you simply prefix the ID with a hashtag (#). Here's how:

HTML code:

p idmyParagraphThis is a paragraph./p

CSS code:

/* Applying styles to the ID */#myParagraph {    font-size: 18px;    color: green;}

Example of Applying CSS to a Class

To apply styles to a class, you prefix it with a dot (.). Here's an example:

HTML code:

button idsomeBtnClick me/button

CSS code:

.someBtn {    background-color: lightblue;    padding: 8px 16px;}

Here, .someBtn is a class, and you can apply a wide range of CSS properties like background-color, padding, and more to it.

Differences Between IDs and Classes

It's important to understand the key differences between IDs and classes:

IDs - Uniqueness

An ID is unique and can only be assigned to one element per page. This means that each paragraph, for example, cannot have the same ID. Here's a valid HTML structure using an ID:

div iduniqueId    Unique content/div

Classes - Non-uniqueness

Classes, on the other hand, are not unique and can be applied to multiple elements. This allows you to apply the same style to different elements or even style a single element with multiple classes:

div classmy_button big green_in_color    Some content/div

In the example above, three classes are applied to a div element: my_button, big, and green_in_color.

Understanding these differences can help you make informed decisions about when to use IDs and classes to style your web pages effectively.