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Updated: 2026年5月31日
Element Width
Original task (JA): 幅を指定
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Conclusion
Element Width — free browser-based HTML/CSS/JS practice
Why it matters in real projects
widthで幅を指定します。 Similar patterns appear daily in code review and production UI work.Step-by-step workflow
1. Read the guide and understand the goal of "Element Width" 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: width, 300. 6. After success, continue with adjacent exercises in the same categoryCore concept explained
widthで幅を指定します。Technical focus
Key HTML elements in this task: div, style.Hint before you peek at the solution
width: 300px;Sample solution walkthrough
The solution uses HTML tags such as div, style. Check nesting and closing tags. CSS properties include width, border. Watch selector spelling and specificity. Explanation: widthで幅を指定します。 Hint recap: width: 300px;Solution code
📝 Sample code
<div>ボックス</div>
<style>div { width: 300px; border: 1px solid #ccc; }</style>Common mistakes for this exact task
・Skipping the hint: width: 300px;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: width, 300. 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 "Element Width" in your own words within 30 seconds ・Practice walking through each line of the sample solution on a whiteboard ・Be ready to discuss tags: div, style ・Discuss CSS properties: width, border ・Prepare one alternative approach and why you chose this oneWhat 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 幅を指定, css-basic, 入門, div, style, width, border, element width—search-friendly guide for Element Width.🧪 Try it here — safe to break things
Use the editor below to write code and preview instantly.
Jump to editor■ Exercise task
divの幅を300pxにしてください。
Hint if stuck
width: 300px;