Create a floating and non-floating back link.

Similiar to http://blog.tagesschau.de/ and many other blogs I have seen, I wish to create a return link to my homepage from my blog, that would show at the top.

I was thinking of having it below the banner either on the right or left: http://blog.joachimheimfeld.de/

Which template file would I need to edit to do this? to show this on every page?

Many thanks for your help.