Ensure the CSS file is correctly linked with a proper href path, .css extension, and placed in the
section; 2. Check for specificity and cascade issues using DevTools, and adjust selectors or use !important sparingly; 3. Fix typos or syntax errors like missing semicolons, unclosed braces, or misspelled values; 4. Clear browser cache or disable it during development to prevent loading outdated CSS; 5. Verify HTML structure matches CSS selectors exactly, including correct classes and IDs; 6. Address display quirks by setting appropriate display properties for elements like inline tags; always use Inspect Element to review applied and overridden styles in the Styles and Computed panels to diagnose issues effectively.Your CSS might not be working for several common reasons. Let’s break down the most likely causes and how to fix them.

1. CSS File Not Linked Properly
Make sure your HTML file correctly links to your CSS file.
? Check:

- The
href
path in the<link>
tag is correct (relative or absolute). - The file extension is
.css
. - The link is placed inside the
section.
<link rel="stylesheet" href="styles.css">
? Tip:
If your CSS file is in a different folder, adjust the path:
<!-- Example: CSS in a "css" folder --> <link rel="stylesheet" href="css/styles.css">
Test the link by intentionally misspelling the filename — if you don’t get a 404 error in the browser’s DevTools (Network tab), the path was likely wrong to begin with.

2. Specificity and Cascade Issues
CSS rules can be overridden by more specific selectors or later rules.
? Examples:
/* This general rule might get overridden */ p { color: red; } /* More specific rule wins */ #main p { color: blue; /* This will apply instead */ }
? How to fix:
- Use browser DevTools (right-click element → Inspect) to see which styles are applied and which are crossed out.
- Increase specificity or use
!important
(sparingly):p { color: red !important; }
- Avoid inline styles if you want external CSS to work.
3. Typo or Syntax Errors
A single typo can break your CSS.
? Common mistakes:
- Missing semicolon
- Unclosed braces
- Misspelled property or value
p { color: blu; /* Typo: should be "blue" */ font-size: 16px /* Missing semicolon */ }
? Fix:
- Use a code editor with syntax highlighting.
- Validate CSS using tools like the W3C CSS Validator.
4. Caching Issues
Your browser may be loading an old version of your CSS.
? Solutions:
- Hard refresh:
Ctrl F5
(Windows) orCmd Shift R
(Mac) - Clear browser cache
- Disable cache in DevTools (under Network tab)
- Add a version query string during development:
<link rel="stylesheet" href="styles.css?v=1.1">
5. HTML Structure Issues
If the CSS targets elements that don’t exist or are misstructured, it won’t apply.
? Check:
- Are the classes or IDs in the HTML matching the CSS?
- Is the element actually on the page?
<!-- HTML --> <div class="header">Hello</div>
/* CSS - must match exactly */ .header { background: yellow; }
? This won’t work:
<div class="header-main">Hello</div>
6. CSS Display or Inheritance Quirks
Some properties don’t apply to certain elements.
? Example:
span { width: 200px; /* Won't work — span is inline by default */ }
? Fix:
span { display: inline-block; width: 200px; /* Now it works */ }
Also, some properties (like height
) don’t inherit — make sure you’re applying them to the right element.
Quick Debug Checklist:
- ? Link tag is correct and in
- ? CSS file loads (check Network tab in DevTools)
- ? No typos in selectors, properties, or values
- ? Selector actually matches an element on the page
- ? No higher specificity overriding your rule
- ? Browser cache cleared
- ? Element is not hidden by
display: none
or similar
Use the browser’s Inspect Element tool — it’s your best friend for figuring out why CSS isn’t applying. Look at the Computed and Styles panels to see what’s being applied and what’s being ignored.
Basically, it’s usually a small mistake — but easy to miss. Take a breath, open DevTools, and walk through each step.
The above is the detailed content of Why is my CSS not working?. For more information, please follow other related articles on the PHP Chinese website!

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