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Troubleshooting CSS

CSS issues can be frustrating, but with a systematic approach you can identify and resolve most problems quickly. This guide walks you through common pitfalls and provides tools to debug effectively.

Common Issues

  • Selector not matching: Check specificity and spelling.
  • Unexpected inheritance: Use all: unset; or stronger selectors.
  • Layout breaking: Verify box model, flex/grid settings.
  • Browser compatibility: Use vendor prefixes or fallback values.

Debug Tools

Modern browsers provide powerful tools for inspecting CSS.

  • Elements panel: View computed styles, toggle properties.
  • CSS Overview (Chrome): Generates a summary of used colors, fonts, etc.
  • Performance tab: Detect reflows/repaints caused by CSS changes.

Step‑by‑Step Diagnosis

1. Verify the selector

Open the Elements panel, right‑click the element, and choose Copy → selector. Compare it with your CSS rule.

.nav > .item.active { color: var(--primary); }

2. Check specificity

Use the Specificity Calculator to see which rule wins.

3. Look for overrides

In the Styles pane, toggle each property to see if another rule overrides it.

4. Test in isolation

Create a minimal HTML snippet and apply the problematic CSS only.

<!-- Minimal Test -->
<div class="test">Hello</div>
<style>
.test { display: flex; color: red; }
</style>

Advanced Techniques

  • CSS Variables Debugging: Use var(--my-var, fallback) to expose missing values.
  • Shadow DOM inspection: Enable Show user agent shadow DOM in DevTools.
  • Print styles debugging: Add @media print { ... } and use the Print preview.

Additional Resources