Please read before order; you may fix it your self :)

5. HTTP Error 401 (Unauthorized)

This error happens when a website visitor tries to access a restricted web page but isn’t authorized to do so, usually because of a failed login attempt.

4. HTTP Error 400 (Bad Request)

This is an error message from the web server telling you that the application you are using (e.g., your web browser) accessed it incorrectly or that the request was somehow corrupted on the way.

3. HTTP Error 404 (Not Found)

Most people are bound to recognize this one. A 404 error happens when you try to access a resource on a web server (usually a web page) that doesn’t exist. Some reasons for this can be a broken link, a mistyped URL, or the webmaster moving the requested page somewhere else (or deleting it). 

2. HTTP Error 403 (Forbidden)

This error is similar to 401, but note the difference between unauthorized and forbidden. In this case, no login opportunity was available. This can happen, for example, if you try to access a (forbidden) directory on a website.

1. HTTP Error 500 (Internal Server Error)

It’s a general-purpose error message when a web server encounters an internal error. For example, the web server could be overloaded and unable to handle requests properly.

Judging by Google’s search statistics, this problem is much more common than 404 errors.