Facebook is a social networking website which allows you to keep in contact with friends, family members, co-workers and former classmates -- and to get back in touch with people from whom you've grown apart over the years. If you navigate to someone's profile and get a "Profile Unavailable" error message, several factors could be to blame.
User Updating Profile
Facebook is a tool users may use 24 hours a day -- and from almost anywhere in the world -- so it's literally always possible for someone to be updating a profile. If you visit a friend's, family member's or anyone else's profile and get the "Profile Unavailable" error, it's possible that person's in the midst of updating. Reload the page five or 10 minutes after you first receive the error, and if you notice any updates displayed on the Wall -- "Jane Doe updated her interests," for example -- this was likely the culprit.
Other types of updates can be to blame for unavailable profiles. Facebook is a utility which constantly upgrades its software, servers and, less frequently, fundamental features and capabilities of user profiles. To prevent the entire site from crashing, however, Facebook must maintain profiles in small groups. As is the case if your friend is updating his or her own profile, it appears unavailable when Facebook is updating the site. Reload the profile after several minutes have passed, and if your friend's Wall doesn't indicate changes were made, Facebook's own site maintenance was behind the profile's temporary unavailability.
If a user decides to no longer be friends with someone, he or she can opt to disable all communications with that user, including the ability to view his or her profile. If you click someone's profile and receive the "Profile Unavailable" error message, it's possible you've been blocked. To assess whether or not this the case, have a mutual friend attempt to access the profile in question. If your friend sees it -- and you conclude your being unable to do so isn't because of personal or sitewide maintenance -- your friend may have blocked you.
When a user violates Facebook's "Terms of Service" for the first time, Facebook may suspend the profile temporarily while its staff investigates the circumstances of the violation. While this investigation is going on, the user's site privileges are temporarily suspended. If neither you nor your friend can access someone's profile and this remains the case for several days, contact that user to see if he or she has been suspended from Facebook. Alternatively, if the user is a repeat offender, Facebook deletes the profile altogether and when you attempt to visit it, you're simply told the profile doesn't exist.
In some instances, your inability to access a friend's profile could simply be due to unplanned errors on the part of Facebook. If you believe this to be the case, report the suspected errors to Facebook using the page it has created for this purpose. Input your friend's name, as well as a short description of steps you've taken to resolve the issue. If you'd like, take a screen shot of the page and attach it to the message, then click "Submit" to send the error report to Facebook.