What's the best way to load custom javascript into a single page?

I wanted to put a simple Javascript in my default.aspx page that will take a random image and place it as a background of a div.  I have the script ready to go but now I'm having trouble understanding where to place it.  I understand I could attach it in the Main.master page but this script is only going to be used in the default page so I didn't want to load it with each page.  

I found a great blog explaining how to Dynamically insert javascript but it's requiring that I can get to the code behind and I don't think I can do that with the default.aspx.  It didn't work when I added the .cs and put a Page_Load method in.

Any suggestions in adding javascript into a page or do I have to load it in the Main.master?