Error code 50019 is displayed when you are using the Chrome monitor and the url you are attempting to test points directly to a Javascript file (e.g. http://cdn.catchpoint.com/js/library.js). Browsers do not execute Javascript files when they are input directly into the address field; instead they just attempt to download the file. The Chrome monitor emulates this behavior, leading to the error message.
To avoid this error, any Javascript you want to test using a browser monitor must be referenced via HTML. Your test configuration would point the HTML resource, and then a <script> tag in the HTML would call the .js file. If you need to test Javascript by direct reference to a .js file, then the Object monitor is the best option.
