I am not familiar with "Office for Mac 2011" but, I would suspect it would be similar with regard to the Page Layout.

With that in mind, check your "Page Setup" menu and make sure in the "Layout" tab of that menu the "Vertical Alignment" is set to "Top".

The only other thing that I can think of is that the Header (if one is applied...you did not specify) may be occupying more space than usual...in which case, you would have to alter that.

Hope this helps...