Well, no, it's the little arrowhead button that appears to the right of the "Post Reply" button that is at the end of the posts on a page. When you click the little arrowhead button, it takes the browser up to the very first post on the page you are viewing. This is most convenient when you have a lot of posts on a page so you dont have to scroll all the way back up to the top of the page in order to navigate the site further.
I've posted a screen shot in the attachment. In this case your post was the last one on the page at the time of this writing.