External CSS is a form of CSS which is used to add styling to multiple HTML pages at a time. It helps to design the layout of many HTML web pages simultaneously. The external CSS is always saved with the .css extension, and through this file, we can change the complete style of our HTML web page.

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What Is CSS?

CSS is an acronym for Cascading Style Sheets. CSS is a design language that enhances the appearance of a website by making it more appealing than plain or uninteresting text. 

CSS vs. HTML

  • CSS determines the visual structure, and layout, whereas HTML mostly determines textual content. 
  • CSS is a style sheet language, and HTML is a markup language. 
  • When we think of CSS, we think of the appearance of HTML pages.

In simple words, CSS improves the appearance of web pages and allows for a more user-friendly layout. The user experience improves when buttons and content are nicely arranged in logical positions.

External CSS

It is one of the most commonly used CSS forms for updating, styling, and modifying the distinctive styles in many HTML web pages at once. An external style sheet can be called into an HTML document using two methods: 

  • Using the <link> tag in the HTML document head. 
  • Using a combination of external CSS functions and integrated CSS. 

One of the unique features of external CSS is that we can write an external style sheet in any text editor, but it should always be saved with a .css extension, and the file must not contain any HTML elements.

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How to Use External CSS?

We use the external style sheet when we wish to make modifications to numerous pages. Using external CSS is excellent for this situation because it allows us to modify the look of the complete website with only one file modification.

It is instrumental when working on big projects or multiple HTML web pages.

To implement external CSS we have to define the filename of the CSS sheet with “mystyle.css” extension within the <link> element inside the <head> section of the HTML page:

<!DOCTYPE html>

<html>

<head>

<link rel="stylesheet" href=mystyle.css>

</head>

<body>

<h1>This is a heading</h1>

<p>This is a paragraph.</p>

</body>

</html>

mystyle.css

In this file, we can write our complete CSS code for styling the HTML web page.

Example:

CSS code for styling border and margin properties inside HTML web page:

p {

  border: 5px  blue;

  margin: 15px;

}

CSS Code for styling border and padding properties inside HTML web page:

p {

  border: 5px  blue;

  padding: 20px;

}

To implement CSS in a particular element of an HTML page, we use .class selector.

.class selector

The .class selector picks up components that have a certain class attribute. Write a period (.) character followed by the name of the class to select components with that class.

.class {

  css declarations;

}

Example 1:

In the below CSS code, .city class selector selects and styles all elements with class =city.

.city {

  background-color: red;

}

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Example 2:

All HTML components with the class="sideway" will be red and center-aligned in this example.

.sideway {

  text-align: center;

  color: green;

}

ID Selector

The id selector uses an HTML element's id attribute to choose a specific element. Because each element's id is unique within a page, the id selector is used to pick just one. 

Write a hash (#) character followed by the element's id to choose an element with a specified id.

Example 1:

This rule will be applied to HTML elements with id=change1.

#change1 {

  text-align: center;

  color: orange;

}

Advantages of Using External CSS

  • For any change in the styling of an HTML page, a single modification to the style sheet can be applied to all the connected pages, resulting in saving time and effort.
  • Selector and grouping techniques are used to apply styles under complex contexts.
  • It helps to keep our code nice and readable as all the code for the styling part is done in a separate file.

Disadvantages of Using External CSS

  • It is not used for small quantities of style definitions.
  • Our page may not function properly until the external CSS file is loaded.
  • To extract styling information from the HTML page, we need to download an extra file.
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Conclusion

External CSS is beneficial for multi-page HTML websites. We can change the complete styling of a website just by changing the code in the .css file, which makes this property of CSS extremely useful for working on large projects. We cannot use this property of CSS in designing a single-page HTML website.

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