I am trying to create a 'back to top' image, it needs to stick to the bottom right corner of the page.

I have created the div with the image but I do not know what is the best way to make it permanently stay at the bottom of the page. Is it best to use absolute positioning?

Also, I want the div to only appear when the user has scrolled past a certain point, and to fade in (or something similar?) 

I have looked online but can't find anything that does what I want. I tried simply getting the div to stick to the bottom but the tutorials I have been using show how to create footers, rather than just one small graphic, so it doesn't work as well.

What are the best practices for this? Any help appreciated!