Everyone, I want you to look at a presentation this way: even if you know only 10% of what there is to know about a topic on which you are presenting, for the most part, that is inextricably more than what your audience knows about the topic. That right there should make your chest stick out at least an inch!
View yourself as the expert, and think that way before and throughout your presentation. It will build you up, and it helps reduce anxiety and lessen your worries about judgment. And another attitude to consider when working to get rid of your nerves and to boost your confidence is if people want to be so judgmental, then they should get up in the front of the room and try to do what you are doing. (Yes. There was some attitude there, but ... well ... that's simply my view on the matter.)