Now go ahead and see if it appears to work (If not jump straight to Step 2 now). If does look like it's working, you are done! Please show me some support by following me on Tumblr to keep up with updates for the code, and also check out my other projects: Scroll To Top Button, which adds the Tumblr Dashboard's "jump to top arrow" to every website you visit such as Facebook or Twitter. And my current project: Videolizer. And follow my music Tumblr: 2N.
If it is now working, posting to your blog with a link to these instructions for others to find would be much appreciated! And if you want to do more, like add a button to your page to let people jump to the top or make your sidebar stay stationary, check out the FAQ.