A guide to make this banner?

[OBE]

How can i make my forumbanner look like this one? (http://www.fitnessprat.no/?styleid=13) A small guide would be nice.. :)

[Floris]

They have a fixed width, which allows them to pick a banner of a certain size.
And instead of 2 column header, they removed the second <td> group from header template.