Lesson 5: Avoiding Common Mistakes

Common Grid Mistakes

Even experienced developers make these mistakes. Learning to spot and fix them will save you hours of debugging.

Mistake 1: Forgetting display: grid

The most common mistake is forgetting to actually enable Grid.

.container {
  grid-template-columns: 1fr 1fr 1fr;
  /* Missing display: grid! */
}

.container {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
}

Mistake 2: Using Commas in grid-template-columns

Grid values are space-separated, not comma-separated.

grid-template-columns: 1fr, 1fr, 1fr;

grid-template-columns: 1fr 1fr 1fr;

Mistake 3: Mixing Up grid-column and grid-template-columns

These are different properties with different purposes.

• grid-template-columns - Defines columns on the container
• grid-column - Places an item within the grid

/* Container */
.grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
}

/* Item */
.item {
  grid-column: span 2; /* Item spans 2 columns */
}

Mistake 4: Percentages with Gap

Percentages do not account for gap space, so use FR units instead.

grid-template-columns: 33.33% 33.33% 33.33%;
gap: 20px; /* Gap breaks the layout */

grid-template-columns: 1fr 1fr 1fr;
gap: 20px; /* Gap is automatically accounted for */

Mistake 5: Using Old Syntax

The old grid-gap property still works, but use the modern gap instead.

grid-gap: 20px;

gap: 20px;

Mistake 6: Not Planning for Mobile

Always test on mobile. Many columns do not work on small screens.

/* Desktop: 4 columns */
.grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

/* Mobile: 1 column */
@media (max-width: 768px) {
  .grid {
    grid-template-columns: 1fr;
  }
}

Mistake 7: Overthinking Alignment

Do not use Grid for centering a single item; Flexbox is simpler.

.center {
  display: flex;
  align-items: center;
  justify-content: center;
}

Debugging Tips

• Use browser DevTools to visualize the grid (Firefox has excellent Grid tools)
• Add a border to items to see their actual size
• Check that display: grid is actually applied
• Verify there are no commas in column or row definitions
• Test on mobile early and often