The JavaScript error "TypeError: null is not an object" occurs when a property is accessed or a method is called on a null value, indicating that an object was expected but not provided. This error message is specific to Safari, while other browsers like Chrome and Firefox display similar errors with different wording. To fix this error, developers should ensure that variables expected to be objects are not null by implementing a check, such as using an if statement before accessing properties. Tools like Rollbar can assist in managing and monitoring these JavaScript errors by providing real-time tracking and analysis, ultimately facilitating a smoother deployment of production code.