Sometimes your website visitors may find that they are unable to view protected documents, since they do not see a login box when clicking on the link to the document, just the message "You need a valid username and password to view this page". This is not a Site Builder fault, but a problem with the setup on the computer used to access the website. It happens when the visitor has previously managed to login and view the document, and stored the access details on the local computer, but those details have become corrupted.
The simplest solution is to install and use another browser to access the document. A different browser will start without the stored username and password so the website will prompt for them to be entered afresh. If the website visitor normally uses Internet Explorer, suggest trying Google Chrome, Mozilla Firefox, or Oracle Opera (which typically offer better performance and a wider range of features than IE).
If this is not acceptable, an alternative is to delete all stored usernames and passwords from Internet Explorer. Unfortunately they cannot be amended or deleted individually. With all other browsers it is possible to delete and/or amend the username/password for an individual web site. See the instructions for Google Chrome, Mozilla Firefox and Oracle Opera.