Hey there! You’re spot-on to suspect the image URL is the main issue here—relative path mismatches are one of the most common pitfalls when setting background-image in CSS, especially when moving from a course’s pre-built structure to your own custom setup. Let’s walk through the key fixes to get that image showing up:

• Verify your relative path structure
  The path in url() is relative to your CSS file’s location, not your HTML file. For example:

  • If your project structure looks like this:

    your-project/
    ├─ index.html
    ├─ img/
    │  └─ battle_for_azeroth.jpg
    └─ css/
       └─ style.css
    

    Your CSS path should be url('../img/battle_for_azeroth.jpg') (the ../ tells the browser to go up one folder from the css/ directory to reach the img/ folder). In your Udemy course, the CSS file was probably in the same root directory as the img/ folder, so url('img/...') worked directly.

• Test with an absolute path
  To rule out relative path confusion, try using a root-relative path (starting with /): url('/img/battle_for_azeroth.jpg'). This points directly to the img/ folder at your website’s root. If the image loads now, you know your original relative path was incorrect.

• Check for case sensitivity and typos
  Many web servers (especially Linux-based ones) are case-sensitive. Double-check that your filename in the CSS matches the actual file exactly—battle_for_azeroth.jpg vs. Battle_For_Azeroth.jpg will cause a mismatch. Also, make sure there are no extra spaces or misspelled folder/filename words.

• Confirm the image exists at the path
  Open your browser’s address bar and type in the full URL to the image (e.g., http://your-local-server/img/battle_for_azeroth.jpg). If the image doesn’t load here, either the file is missing from that folder, or the path is wrong.

Once you fix the URL path, your existing CSS properties (background-size: cover, background-position: center, etc.) should work just like they did in the course!

内容的提问来源于stack exchange，提问作者Buckyx55