To teach web safety, I use Netsmartz.org. This website is dedicated to teaching students (and adults that work with young children) digital safety and citizenship. This Bad Netiquette Stinks lesson is especially geared toward empathetic behavior and building positive relationships online.
When we do our research units, we really discuss how not everything you find online is necessarily fact. We discuss that you should always use a trusted source, and we use PebbleGo as our trusted place to get information.
Before students are given their iPads, we do several Netsmartz.org lessons and watch the accompanying videos. The videos and lessons are very kid friendly and present topics such as netiquette, password protection, talking to/giving information to strangers, cyber-bullying, what to look for when deciding whether to trust websites or open files, and other internet safety topics. We go over each of these concepts in depth, and then students sign an internet safety contract. They are then eligible to receive their iPad. Our NetSmartz rules are posted in the classroom for constant reference.
I use this lesson from Netsmartz.org to teach students about protecting their personal information while online. They discuss the dangers of sharing personal information and finish by writing a paragraph describing what they will do if a 'Follow-You Fiona' tries to contact them online.