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First CSS stylesheet

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Introduction

CSS stylesheets help make web pages look nice and organized. They control colors, fonts, and layout.

You want to change the color of text on your webpage.
You want to make headings bigger or smaller.
You want to add space around images or text.
You want to set a background color for your page.
You want to make your website look good on phones and computers.
Syntax
CSS
selector {
  property: value;
}

Selector chooses which HTML parts to style.

Property is what you want to change, like color or font size.

Examples
This sets the whole page background to light blue.
CSS
body {
  background-color: lightblue;
}
This makes all <h1> headings dark red and bigger.
CSS
h1 {
  color: darkred;
  font-size: 2rem;
}
This adds space above and below paragraphs and makes lines easier to read.
CSS
p {
  margin: 1rem 0;
  line-height: 1.5;
}
Sample Program

This example shows a simple webpage with a linked CSS file named styles.css. The CSS sets a light blue background, changes the font and colors, and styles the heading and paragraph for better readability.

CSS
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <title>My First CSS</title>
  <link rel="stylesheet" href="styles.css" />
</head>
<body>
  <h1>Welcome to My Website</h1>
  <p>This is my first CSS stylesheet example.</p>
</body>
</html>

/* styles.css */
body {
  background-color: #f0f8ff;
  font-family: Arial, sans-serif;
  color: #333333;
  padding: 1rem;
}
h1 {
  color: #00509e;
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
}
p {
  font-size: 1.125rem;
  line-height: 1.6;
}
OutputSuccess
Important Notes

Always link your CSS file inside the <head> section using <link rel="stylesheet" href="filename.css" />.

Use readable font sizes with rem units for better accessibility.

Test your styles on different screen sizes to make sure your page looks good everywhere.

Summary

CSS stylesheets control how your webpage looks.

Use selectors to pick HTML elements and properties to style them.

Link your CSS file in the HTML <head> to apply styles.

Practice

(1/5)
1. What is the main purpose of a CSS stylesheet in web development?
easy
A. To control the appearance and layout of HTML elements on a webpage
B. To add interactive behavior to webpage elements
C. To store data for the webpage
D. To write the content of the webpage

Solution

  1. Step 1: Understand CSS role

    CSS is used to style and arrange how HTML elements look on a page.

  2. Step 2: Differentiate from other web technologies

    JavaScript adds behavior, HTML holds content, CSS controls style and layout.

  3. Final Answer:

    To control the appearance and layout of HTML elements on a webpage -> Option A

  4. Quick Check:

    CSS = style control [OK]
Hint: Remember: CSS styles, HTML structures, JS acts [OK]
Common Mistakes:
  • Confusing CSS with JavaScript functionality
  • Thinking CSS stores webpage content
  • Believing CSS adds interactivity
2. Which of the following is the correct way to link an external CSS file named styles.css in an HTML document?
easy
A. <link rel="stylesheet" href="styles.css">
B. <style src="styles.css"></style>
C. <script src="styles.css"></script>
D. <css href="styles.css">

Solution

  1. Step 1: Identify correct HTML tag for CSS linking

    The <link> tag with rel="stylesheet" and href attribute is used to link CSS files.

  2. Step 2: Check other options for correctness

    <style> tag does not use src, <script> is for JavaScript, <css> is invalid HTML.

  3. Final Answer:

    <link rel="stylesheet" href="styles.css"> -> Option A

  4. Quick Check:

    Use <link rel="stylesheet"> to link CSS [OK]
Hint: Link CSS with <link rel="stylesheet" href="file.css"> [OK]
Common Mistakes:
  • Using <style> tag with src attribute
  • Using <script> tag for CSS
  • Writing invalid tags like <css>
3. Given the CSS below, what color will the paragraph text be?
p { color: blue; }
p.special { color: red; }

And the HTML:
<p class="special">Hello!</p>
medium
A. Blue
B. Red
C. Black (default)
D. Green

Solution

  1. Step 1: Understand CSS selector specificity

    The selector p.special targets paragraphs with class "special" and overrides p styles.

  2. Step 2: Apply styles to the HTML element

    The paragraph has class "special", so it uses the color red from p.special.

  3. Final Answer:

    Red -> Option B

  4. Quick Check:

    More specific selector wins = red [OK]
Hint: Class selectors override element selectors [OK]
Common Mistakes:
  • Ignoring class selector specificity
  • Assuming first rule always applies
  • Confusing color names
4. What is wrong with this CSS code?
body {
  background-color: #fff
  color: black;
}
medium
A. Using body selector is invalid
B. Incorrect color value for background-color
C. Missing semicolon after background-color property
D. Properties should be inside <style> tags

Solution

  1. Step 1: Check CSS property syntax

    Each property must end with a semicolon except the last one, but here background-color is not last and misses semicolon.

  2. Step 2: Validate other parts

    Color value #fff is valid, body selector is valid, CSS can be inside external or style tags.

  3. Final Answer:

    Missing semicolon after background-color property -> Option C

  4. Quick Check:

    Every CSS property line needs semicolon [OK]
Hint: Check semicolons after each CSS property line [OK]
Common Mistakes:
  • Forgetting semicolons between properties
  • Thinking #fff is invalid color
  • Believing body selector is wrong
5. You want all <h1> headings on your page to be green, but only those inside a <section> should be bold. Which CSS code achieves this?
hard
A. h1 { font-weight: bold; }
section h1 { color: green; }
B. h1 { color: green; font-weight: bold; }
section h1 { color: green; }
C. section h1 { color: green; font-weight: bold; }
h1 { font-weight: normal; }
D. h1 { color: green; }
section h1 { font-weight: bold; }

Solution

  1. Step 1: Set all h1 color to green

    The rule h1 { color: green; } colors all h1 headings green.

  2. Step 2: Make only h1 inside section bold

    The rule section h1 { font-weight: bold; } targets only h1 inside section and makes them bold.

  3. Final Answer:

    h1 { color: green; } section h1 { font-weight: bold; } -> Option D

  4. Quick Check:

    General style first, then specific override [OK]
Hint: Style all, then add specific inside selector [OK]
Common Mistakes:
  • Applying bold to all h1 instead of only inside section
  • Overwriting color unintentionally
  • Using wrong selector order