Default page – Not found

I got WordPress up and running, but after deleting some posts and rewriting them as pages instead, I now get this error message, when I go directly to my domain:

Not Found

Apologies, but no results were found for the requested archive. Perhaps searching will help find a related post.

How can I set the default page which will be loaded?

/Edit/
Solved it, stupid of me not to try to make a new page, which will then show up on the first page. But is it possible to keep that post there, so that any new posts or pages I make do not replace it?