Page-relative references are death in web applications. Use server-relative references that begin with the context path.
Think about it for a minute: the browser is trying to find the image file in the file system relative to the current URL. That's fine in a static site where the URLs represent folders. But in a web app, the URLs are mapped and have nothing whatsoever to do with the file system.
By removing the .. you got it to accidentally work. Don't depend upon that. Use server-relative addresses as outlined in this JSP FAQ.