i was using codesandbox for school and i lost 3 hours of work on a file its due tommorow please reply with help
Firstly, welcome to the forums.
While we are primarily here to help people with their Free Code Camp progress, we are open to people on other paths, too. Some of what you are asking is pretty trivial in the Free Code Camp context, so you might find that if you’re not getting the instruction and material you need in your current studies, the FCC curriculum will really help you get started. At a modest guess I’d say investing a 4-5 hours working through the curriculum here will really pay off. You can find the curriculum at https://www.freecodecamp.org/learn.
With your current questions, we don’t have enough context to know what you already know or don’t know, so it is impossible to guide you without just telling you the answer (which we won’t do).
It is pretty typical on here for people to share a codepen / repl.it / jsfiddle example of what they have tried so that anyone helping has more of an idea of what help is actually helpful.
Please provide some example of what you’ve tried and I’m sure you’ll get more help.
Happy coding 
thank you, I was coding for school, and I was only putting pictures and text. i left the computer open and took my dog out for 5-10 minutes i came back and it looked like this
the code was gone but the preview stayed until refresh then it went blank
could you also tell me how to access previous versions of the file?
did you make commits? if you didn’t I have no idea
what are commits? (can you explain please?)