Help:How to revert a page to an earlier version
Why pages should be reverted
Spamming is quickly turning into the number one reason why pages should be reverted. Spamming is when a page is suddenly filled with advertising links. As of this writing, cacheopedia does not support advertised linking.
If the edit does nothing to enhance the page, or is 100% wrong information, a revert is justified.
How to do it
If you are in the recent changes page, and see an edit, you can always hit the diff link to see what the changes were for that edit. If you happen to be a sysop of this wiki, there will be a roll back link on the diff page. This is different from just doing a regular edit to remove the offending material, and the preffered method.
Also, there is a user contributions page for each user or ip address. If you click on an IP address in the recent changes page, you will go to it. You can view diffs for that user or do rollbacks right from there. You can get to user contributions from a registered user's profile page.
See also Wikipedia:revert