Looks like the class "fancybox-active compensate-for-scrollbar" is causing it, and specifically the rule "margin-right: 17px;" is pushing everything to the right. Give tweaking that go, and let me know if that works!
Thank you a lot for the suggestion! Sorry, but I'm having a lot of trouble finding the "margin-right: 17px;" rule you found haha, I keep using control f but nothing comes up. Is it in the js file or the css file?
I've now added another section on my Guestbook page where people can put down their website or email address if they so wish, this way if someone has a question for me I can answer them! The name and contact sections on my Guestbook are optional, so anyone can also send anonymous messages if they prefer c: