Read the HTML Reference page. If you make a Wiki link to a page that doesn't exist, you can then edit the content on that page, creating an entirely new page.

We also have revision control and page locking capabilities. No one can "delete" a page. If a page is editted and a link removed, you can add the link back, the page will still be there. If an edit is made that blanks a page, we can roll that edit back. there's an Alert an Admin feature on every page if you see something like this.

You can also subscribe to pages, so that you recieve a notice when they change. You can do this from the "Change Content" form.