This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Both of those approaches, absolute paths as well as page-relative paths are poor ways to specify the path to a resource in a Java web app. See the ServletsFaq for more information on types of paths and why you should be using a server-relative path.
Page-relative URLs are relative to the current URL, not the "current folder" (of which there is no real concept). URLs in web apps are mapped, so they don't actually represent any folder structure. So they are fragile and should not be used.