Google had first indexed my website two weeks after it was published, and placed it at the fifth page, somewhere.
Three days later the website was promoted to the second page, last place.
Three days later it was pushed down to the third page, last place.
And now (a week later) it appears at the fourth page, somewhere in the middle.

What's the reason for this fall?
And what should I do in response?

During that peroid, I got new incoming links (although google doesn't show them in "links:" command.
Also I updated the website from time to time.. not alot, but it wasn't too static.

What do you think?

PS, can I mention the website address here?