I created a custom masterpage and a content page based on it in SPD for a
publishing site and when an administrator views the page, it looks ok.

But when it is viewed by a regular user, he dosesnt see anything in the
contentplaceholder area...He simply doesnt see any of the webparts added by the
admin. Any ideas on why this happens?

I googled this up and found that the problem could be due to the page not being
published.

The problem with that is that the publishing tag was included on the masterpage
but it simply doesnt show up.