What Is a 403 Forbidden Error?
In computing terms, machines that store website files for other computers to access are called servers. Computers that attempt to access these files are called "clients," and each attempt is called a "request." After receiving a request, the sever sends back one of a large number of responses. These responses are identified by a status code, and they tell the client whether the request was successful, and if not, why not. A HTTP 403 Forbidden message is one of these status codes.
All status codes beginning with a number 4 are classified as error codes. Specifically, they refer to errors that originated with the client, such as requesting a Web page or other resource that does not exist, which is a 404 error. A 403 error indicates that a request was sent and understood by the server, but the server has refused to respond for some reason. This is classified as a client-side error because with a 403 error, the server does not have to give a reason for refusing access.
Looking at the HTML Web pages is not the only way of browsing websites. It is also possible to view all the files of a web page in directory format, which is just the same way files are browsed on a local computer, such as through Finder on a Macintosh, or Explorer on Windows. However, because this can be used for malicious purposes, it is usually disabled on websites. If a client attempts to browse a site's directory structure, usually a 403 response is received.
Sometimes a 403 error will be given after attempting to access a website's normal Web pages. A common cause of this is malicious software which had been secretly installed on the computer, perhaps via other infected software or email attachments. Malware programs might attempt to browse the directory structure of sites you visit normally, and when the request is received by the server it sends back a 403 error, both to you and the malware program.
Solving 403 Errors
The first step is to log in to any networks on which the resources you are trying to access are located. If you are logged out and attempt to access an internal resource or webpage, a 403 error might be returned. If you are logged in, check your system for malware using an anti-virus program. To check whether your IP address is blocked, attempt to access the resource via a proxy. If this works, contact the network administrator, or if you do not have a static IP, try again later in the day.