Oh Boy!

So I was trying to install a new cute blog background and somehow ended up deleting the HTML/Java script thing were you are supposed to copy and paste your blog background. Now it is gone and I don't know how to get it back. So I put a new background, using a different template so it wouldn't be blank at least. It is not very cute and I think I would have been better off not trying to make my blog look better. Now I am just frustrated and don't know how to get it back? Anyone know? If not my blog may be ugly forever! :)