The "Invalid CSS after..." error is one of the most common issues developers may encounter when working with CSS preprocessors such as Sass or Less. This error typically occurs when the syntax of CSS code is incorrectly formulated, resulting in compilation failure. In this article, we'll explore the causes of this error and offer several solutions to effectively address it.

Identifying the Problem

The error message "Invalid CSS after..." usually provides information about where exactly in the code the error occurred. Here's an example of the error message:

Invalid CSS after "p {color: #333;": expected "}", was ""

In this example, the error message indicates that the closing curly brace } is missing after the declaration p {color: #333;, which is necessary for proper CSS syntax.

Causes of the Error

The "Invalid CSS after..." error can occur due to several reasons:

1. Missing Closing Curly Brace - As indicated in the example, the most common cause is a missing closing curly brace.
2. Incorrect Use of Variables - In preprocessors like Sass, improper usage of variables can also lead to this error.
3. Inconsistent Indentation - In Sass, which relies on indentation for defining nesting, inconsistent indentation can cause syntax errors.
4. Syntax Errors - Other syntax errors, such as missing semicolons or typos in property names, can also result in this error.

Resolving the Issue

Fixing the "Invalid CSS after..." error depends on its root cause. Here are some steps you can take:

1. Review and Correct Syntax - Carefully go through the line of code mentioned in the error message and fix any syntax errors.
2. Check Curly Braces - Ensure that every opening brace has its corresponding closing counterpart.
3. Verify Variables - Check that all variables are properly declared and used.
4. Normalize Indentation - Make sure indentation in the code is consistent, especially when working with preprocessors that rely on indentation.

The "Invalid CSS after..." error can be frustrating, but it typically signals a minor syntax error in your code. By meticulously reviewing and fixing the faulty parts of the code, this error can be quickly resolved. It's important to maintain a systematic approach to debugging and keep in mind the common causes outlined in this article.