Introduction

CSS looks simple, but beginners often make mistakes that affect layout, responsiveness, and UI quality.
Diffcozen lists the most common CSS mistakes and how you can avoid them.

1. Not Understanding the Box Model

Many beginners don’t fully understand padding, margin, and border.
This causes layout issues, uneven spacing, and broken UI.

2. Using Wrong Units

Using px everywhere leads to poor responsiveness.
Use:

• rem
• em
• vw & vh
• clamp()

3. Overusing !important

When developers don’t understand specificity, they rely on !important.
This makes CSS hard to maintain.

4. Not Using Flexbox or Grid

Relying on float layouts is outdated.
Modern layout = Flexbox + Grid.

5. Not Writing Reusable Classes

Instead of repeating code:

.text-center {
  text-align: center;
}

Write utility classes for consistency.

6. Ignoring Responsive Design

Design must work on:

• Mobile
• Tablets
• Desktop

Use media queries and fluid units.

Conclusion

Avoiding these mistakes will help you write professional CSS.
Diffcozen teaches all modern CSS concepts through live projects.