Permamarks is a free tool that “freezes” the content you bookmark on the web with a date / time stamp. This includes files.
Each saved page has a permanent, uneditable URL that can be shortened and customized. You can also organize your bookmarks into lists.
Permamarks provides users “integrity of links.” Even if a page you are linking to is edited or removed, you preserve the exact page for when you captured it. This means no more dead links, or 404 page errors.
(Source: Permamarks Blog)
Permamarks is in invite mode right now. Get on the waiting list by visiting https://permamarks.com.