Edit: Proposed addition to this FAQ:
If none of your friends have updated their journals within the last two weeks, you will not see any entries on your friends page. The friends page only shows entries made within the last two weeks. You can view your friends' older entries by visiting their journal's recent entries page (http://www.livejournal.com/users/exampleusername).
If your friends have updated within the last two weeks, they may have protected entries which you are not able to see. If you are on a user's friends list and believe you should be able to see friends only entries on your friends page you should check to make sure you are logged into LiveJournal (http://www.livejournal.com/login.bml). If you are having trouble staying logged into LiveJournal, instructions on how to fix this can be found at http://www.livejournal.com/support/faqbrowse.bml?faqid=162.