In design view, select the entire apDiv7 div. In the CSS panel, delete the 'position' property. With the div still highlighted, ctrl + X to cut it, place your cursor where you want it to go, then ctrl + V to paste it in.
Select the div again, and in the CSS panel add the property 'margin' = auto.
You may want to remove one or more of the ' ' (spaces) and add top and bottom margins for exact horizontal positioning.