Header 1 and 2 alignment

I have template dimensions settings of 940px wide and header 1 as 520px (in the template setup).

My header one photoslide displays fine. However, whichever module I assign to Header2 drops to the space below header 1 (why?) and to the right (expected).

I have inserted different modules, including a picture in custom HTML to ensure that I have not created content which is too large.

I understand from other forum entries that header2 width is template width less header 1 width.

Could you explain why the position "drops" and how to ensure it remains beside header 1?