In HTML, a CSS file is used to style the content of a web page. However, in the open-source development environment Java IDE, IntelliJ IDEA, CSS404 error message is displayed when a user tries to style a web page in the editor. This error message indicates that the CSS file that is being used for style is not found or is not accessible.

The error message "CSS404: No such file or directory" can be troubleshoot by looking at the file system path where the CSS file is being stored. If the CSS file is not in the correct location, the error message will be displayed. If the CSS file is in the correct location, but the file is not found, the error message will be displayed.

In some cases, the problem may be caused by a network error or a server error. To troubleshoot this error, the user should first check the network connection and make sure that the user is able to reach the server where the CSS file is located. If the network connection is good, but the file is still not found, the user may need to check the server's file system to ensure that the CSS file is accessible.

To resolve this issue, the user should check the file system and make sure that the CSS file is accessible. They may need to create a new directory or move the file to a different location to make it accessible. If the problem is caused by a server error, the user should contact the server administrator to request an update or to clarify the file location.

In summary, the error "CSS404: No such file or directory" in IntelliJ IDEA indicates that the CSS file that is being used for style is not found or is not accessible. To troubleshoot this issue, the user should check the file system and make sure that the CSS file is accessible. If the file is not accessible, the user should check the server's file system to ensure that the file is accessible. If the problem is caused by a network error or a server error, the user should check the network connection and make sure that the user is able to reach the server where the CSS file is located.