../ is a bookmarklet for travelling up in the directory tree on any site. Drag it to your bookmarks toolbar, then test fire it for example on this very page; you should see the contents of the directory this page resides in. Click it again and you should be moving further up in the directory tree (although with the latter you'll immediately get redirected onto the site's front page as I've hidden the root of my storage directory from direct viewing).
As you can see, the function of the bookmarklet is that of either (roughly) cd . or cd .., depending on your current location. If you're looking at a page whose URI does not end in a slash, on your first click of the bookmarklet you'll be taken to the root of the current directory. When you're at the root of a directory (that is, looking at a page whose URI ends in a slash), a click of the bookmarklet will move you one directory level upwards.
The bookmarklet has been tested using Firefox only. If you have any comments, you can drop them to me over at my blog.