Template:Outdated
The purpose of this template should be obvious: tag pages whose content is no longer valid and should not be used any further. Pages tagged with this will be included in the Category:Deprecated pages and will display the contents of the page in a pinkish-color as a reminder for the whole (just in case there are links tu subsections that fail to make the warning visible. It also removes the [Edit] links in the subsections to avoid further editions (although it does not protect the page).
There's another related template Template:Dated which should be used for pages with stale or otherwise out-of-date information—but that in general just needs an update.
The template takes an extra (optional) parameter that can basically be any text and will be displayed right after the warning sign.
{{Outdated |some text pointing to [[The OLPC Wiki|alternative page]] or just text.}}