You're going to have to use a third party service like smartgb.com for your guestbook, I'm afraid. Neocities doesn't support server-side scripting like PHP.
afaik, sadgrl is able to have a php guestbook because she uses leprd.space. Here's her tutorial on setting up your own guestbook this way: https://learn.sadgrl.online/php-project-building-a-guestbook/ . Bear in mind, I've tried this method myself and was never able to get it off the ground (I don't think leprd.space is accepting new users at this time.)
hey hey I'm late to the party but what the others said is true! if you have any specific questions about building one in php/sql, feel free to shoot me an email (it's on my about page!)
Hey there! At the risk of a super long comment that definitely won't fit on here, this method of adding a background is very complex and cannot be easily used with my layout maker. My layout maker accepts images as backgrounds. I tried copying the code from the starry sky tutorial directly to a CodePen and it didn't work because the CSS references two images, which are included if you click on "Download" at the top.
CSS references 4 images* topleft, topright, bottomleft, bottomright.
dang, was hoping it would be easy. thanks for giving it a try, though!