Facebook rolled out its newest version in September 2011; some users have since experienced problems logging in to Facebook, particularly when using certain Web browsers.
How to Log In
The first step in avoiding errors during the login process is to make sure you are doing it correctly in the first place. Type the complete Facebook homepage URL into your Web browser; using a cached address may lead to problems, particularly with certain browsers. Type your user name -- typically the email address you used to sign up for your Facebook account, unless you changed this information in your account settings -- and your password before pressing the login button next to the text boxes.
"Not Logged In" Error
This problem occurs when you log in to Facebook, then open multiple tabs on your Web browser. For example, you log in to your home page and then want to check out the profiles of three friends by opening a new browsing tab for each one. If you log out of Facebook on one of the tabs and then try to click over to another open tab, a pop-up message will appear on your screen, telling you that you are "Not Logged In." You'll be prompted to reenter your user name and password to continue browsing the open Facebook tabs, even though you did not log out of Facebook on those specific tabs.
Avoiding the "Not Logged In" Error
Look underneath the user name and password text boxes on your Facebook login page and you'll find a box next to the words "Keep me logged in." Checking this box will keep you logged in to Facebook even if you close tabs, close your Web browser or log out of Facebook accidentally on one tab while Facebook is still open in another. Internet Explorer 7 has had compatibility issues with this function, however; click on the "Tools" tab and select "Internet Options" from the drop-down box. Click on "Security," then "Custom Level." Locate the "User Authentication" option and choose "Automatic login with current user name and password" from the list to change your browser's settings to allow Facebook to keep you logged in.
Google Chrome Errors
Recent updates to Facebook have at times wreaked havoc on members using Google Chrome as their Web browser. This is primarily a cache issue. If you're having issues logging in to Facebook using Google Chrome, click on the wrench in the upper right corner of the Google Chrome toolbar and click "Options" from the drop-down box. Select "Under The Hood" from your list of options, then "Clear Browsing Data" to clear Chrome's cache. Facebook's help center also reports that a message that reads "Must be logged in to view this page" has been reported by some users. Facebook urges members who have experienced this problem to report it to the site's technical support staff.