When you start a new relationship, there are many things you don't know about your partner. You'll learn a lot in the course of dating, but there'll be a few uncertainties in the meantime. If you worry about those uncertainties, though, it might lead to negative emotions of suspicion and paranoia, and ultimately to the relationship risk known as jealousy.
Facebook can magnify worries by encouraging you to indulge your suspicions. Facebook constantly reveals your partner's friends, likes and comments. If the relationship is new, or if you haven't yet developed a good trust with your partner, you might scrutinize each message looking for evidence to confirm or deny your suspicions.
Don't let worry get the best of you on Facebook. While the relationship is new, listen to your partner and don't rush to a hasty judgment about any conversations you read. Take time to learn how your partner interacts with other friends online. You might learn that your partner is often sarcastic, cheeky or ironic when talking to friends, with statements that are only suspicious when taken out of context.
If you're still concerned, don't post that concern to Facebook. This can come across as jealousy, and it can erode any trust you've built up with your partner so far. Instead, on your next date, ask for more information about what worried you, and listen to the answer. There may be a lot more to the conversation than you could have known without asking.