Creating a Back To Top button makes it easier for your readers and you to get back on the top of your page. This button is advisable especially to blogs with long posts or homepages which contains many topics/articles. When your readers and you are at the button of a blog's page, isn't it better to just click the Back To Top button than to scroll all the way up?

Anyway, creating your Back To Top button is easy. Just copy this code and paste it on your blog's layout's HTML/JavaScript section (Dashboard --> Layout --> Add A Gadget --> HTML/JavaScript):
Things to remember:

Never change # to anything else. Your button will not work if you change it.

Place your Back To Top button's image by copying the image location of your photo (not the COPY LINK LOCATION). You can always look for some icons over the net or google for some. If you want to create personalized Back To Top buttons on PhotoBucket (and other image hosting sites), just copy the Direct Link To Image then replace the code's direct link to image with your image's link. 

That's it. just save it and you already have your page's Back To Top navigator.

You can also create other useful floating buttons together with your Back To Top icon. Check the tutorial here.