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Updated: 2026年5月31日

Background Color

Original task (JA): 背景色

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Conclusion

Background Color — free browser-based HTML/CSS/JS practice

■ What this exercise teaches bodyの背景色を#f5f5f5にしてください。

Why it matters in real projects

background-colorで背景色を指定します。 Similar patterns appear daily in code review and production UI work.

Step-by-step workflow

1. Read the guide and understand the goal of "Background Color" 2. Review the HTML/CSS/JS editor pane and start from the starter code 3. Open hints if stuck; compare your diff with the sample solution 4. Click Run and inspect preview/console output 5. Auto-check looks for output containing: background, f5f5f5. 6. After success, continue with adjacent exercises in the same category

Core concept explained

background-colorで背景色を指定します。

Technical focus

Key HTML elements in this task: style.

Hint before you peek at the solution

background-color を使います。

Sample solution walkthrough

The solution uses HTML tags such as style. Check nesting and closing tags. CSS properties include background-color. Watch selector spelling and specificity. Explanation: background-colorで背景色を指定します。 Hint recap: background-color を使います。

Solution code

📝 Sample code
<style>body { background-color: #f5f5f5; }</style>

Common mistakes for this exact task

・Skipping the hint: background-color を使います。

Troubleshooting

Q: Preview does not change after Run A: Ensure you edited the HTML/CSS/JS pane and clicked Run. Q: Looks correct but check fails A: Auto-check looks for output containing: background, f5f5f5. Look for typos, full-width spaces, or unclosed tags. Q: Console shows errors A: Open DevTools Console and fix bracket/quote mismatches at the reported line. Q: Hard to type on mobile A: Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.

Interview / portfolio tips

・Explain the techniques in "Background Color" in your own words within 30 seconds ・Practice walking through each line of the sample solution on a whiteboard ・Be ready to discuss tags: style ・Discuss CSS properties: background-color ・Prepare one alternative approach and why you chose this one

What to do after you pass

Move to the next exercise in the css-basic track, then continue the learning roadmap at /en/learning/css-basic/.

Keywords

Free hands-on exercise covering 背景色, css-basic, 入門, style, background-color, background color—search-friendly guide for Background Color.

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■ Exercise task

bodyの背景色を#f5f5f5にしてください。

Hint if stuck

background-color を使います。

10pt

背景色

bodyの背景色を#f5f5f5にしてください。

エラーをクリックで該当行をハイライト。✕=エラー ⚠=警告 ›=ログ。

Roadmap · All guides

Deep dive

"Background Color" is a 入門-level HTML/CSS/JS exercise. bodyの背景色を#f5f5f5にしてください。 Run it in-browser with automatic checking.

background-colorで背景色を指定します。 Similar patterns appear daily in code review and production UI work.

Pair this with the css-basic roadmap. Exercise #17 reinforces core css-basic skills.

Step-by-step workflow

  1. Read the guide and understand the goal of "Background Color"
  2. Review the HTML/CSS/JS editor pane and start from the starter code
  3. Open hints if stuck; compare your diff with the sample solution
  4. Click Run and inspect preview/console output
  5. Auto-check looks for output containing: background, f5f5f5.
  6. After success, continue with adjacent exercises in the same category

How to read the sample solution

The solution uses HTML tags such as style. Check nesting and closing tags. CSS properties include background-color. Watch selector spelling and specificity. Explanation: background-colorで背景色を指定します。 Hint recap: background-color を使います。

Real-world & career relevance

CSS basics underpin designer collaboration and frameworks like Tailwind. Color, spacing, and type define brand consistency.

Common mistakes

  • Skipping the hint: background-color を使います。
  • Confusing margin and padding
  • Missing # in hex colors
  • Forgetting . for class selectors

Troubleshooting

Preview does not change after Run
Ensure you edited the HTML/CSS/JS pane and clicked Run.
Looks correct but check fails
Auto-check looks for output containing: background, f5f5f5. Look for typos, full-width spaces, or unclosed tags.
Console shows errors
Open DevTools Console and fix bracket/quote mismatches at the reported line.
Hard to type on mobile
Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.

Interview & portfolio tips

  • Explain the techniques in "Background Color" in your own words within 30 seconds
  • Practice walking through each line of the sample solution on a whiteboard
  • Be ready to discuss tags: style
  • Discuss CSS properties: background-color
  • Prepare one alternative approach and why you chose this one

Glossary

color
CSS property for text color.
padding
Inner spacing inside an element.
margin
Outer spacing around an element.

Keywords covered on this page

Free hands-on exercise covering 背景色, css-basic, 入門, style, background-color, background color—search-friendly guide for Background Color.

Related dev tools

Learning roadmap

Learning roadmap →

Related exercises

Frequently asked questions

Is "背景色" free?

This exercise is free and runs entirely in your browser. No account or credit card required.

Difficulty and time?

"背景色" is level "入門". Read the guide first; beginners can usually finish within 30 minutes. Allow 5–15 minutes per exercise. Use hints, then the solution if stuck.

What after a correct answer?

After a correct answer, use "Next exercise". When you finish a category, continue on the learning roadmap.

Works on mobile?

Works on mobile browsers, but typing code is easier on a desktop.

Where are other exercises?

All exercises: /en/learn/ with category filters.

Key takeaway for "背景色"?

background-colorで背景色を指定します。 Hint: background-color を使います。

Where does css-basic fit?

CSS basics underpin designer collaboration and frameworks like Tailwind. Color, spacing, and type define brand consistency.

Step-by-step for "Background Color"?

1. Read the guide and understand the goal of "Background Color"
2. Review the HTML/CSS/JS editor pane and start from the starter code
3. Open hints if stuck; compare your diff with the sample solution
4. Click Run and inspect preview/console output
5. Auto-check looks for output containing: background, f5f5f5.
6. After success, continue with adjacent exercises in the same category

How to read the sample solution?

The solution uses HTML tags such as style. Check nesting and closing tags.

CSS properties include background-color. Watch selector spelling and specificity.

Explanation: background-colorで背景色を指定します。

Hint recap: background-color を使います。

Something is not working?

Preview does not change after Run → Ensure you edited the HTML/CSS/JS pane and clicked Run.
Looks correct but check fails → Auto-check looks for output containing: background, f5f5f5. Look for typos, full-width spaces, or unclosed tags.
Console shows errors → Open DevTools Console and fix bracket/quote mismatches at the reported line.
Hard to type on mobile → Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.

Career / interview angle?

Explain the techniques in "Background Color" in your own words within 30 seconds Practice walking through each line of the sample solution on a whiteboard Be ready to discuss tags: style Discuss CSS properties: background-color Prepare one alternative approach and why you chose this one

Can I change the starter code?

Yes—if it works. Understanding the starter first, then adding minimal diffs, speeds up learning.

What do the points mean?

10pt is a difficulty hint, not a score you must maximize.