-: Missing closing tags breaks layouts.

Inline styles clutter HTML.

Not testing on multiple devices hides issues.

Copy-pasting without understanding causes bugs.

Skipping version control or leaving debug logs complicates fixes. These are common early mistakes. Practice cleaning up code, using stylesheets, testing responsively, and tracking changes. Soon, your workflow will improve and you’ll avoid these pitfalls naturally. Remember to comment wisely, validate inputs, and keep learning with small steps.