JavaScript's "script error" occurs when an exception violates the same origin policy of a browser, which is a security measure to prevent scripts from different domains from executing on a webpage. This error typically appears in response to the onerror callback when the necessary request headers are not met. To resolve this issue, developers can set up Cross-Origin Resource Sharing (CORS) headers, such as Access-Control-Allow-Origin, to allow resources to be accessed from any domain or specific domains. Additionally, setting the crossorigin attribute to "anonymous" in HTML scripts can help by instructing the browser to fetch resources without transmitting user-identifying information. This guidance aims to assist developers in troubleshooting and resolving script errors in JavaScript effectively.