They are frustrating and maddening. And, sometimes you want to pull your hair out. Although error messages are unavoidable and a part of the experience of using the Internet, possessing an understanding of what they mean can be of valuable assistance in getting the most from your endeavors.
Web addresses are case sensitive.
Be sure to watch for commas instead of periods. Something is wrong with the URL you entered. Check your typing, expecially special characters like slashes and colons as well as uppercase letters. If you entered a password, you may have typed it incorrectly. Passwords are, also, case sensitive.