They're frustrating. Maddening. But, while error messages are an unavoidable (if occasional) part of the Internet, knowing what they mean can often help you get around them.  

Generally, when you get an error message, you should first try hitting the Refresh/Reload button — twice. Then, check that you entered the URL correctly. Remember, URLs are case-sensitive. And watch for commas instead of periods. Also, if you cut and pasted the URL into the Location/Address field, make sure you got the full URL. While you don't need to enter http:// to get to Web sites anymore, mistakenly typing ttp:// will definitely give you an error message.