Hi again Sayontan,
I believe Eric and I are having the same issue.
What I want is exactly what you see in my header as it is, except that the right image (ad) needs to be clickable. I would have thought the place to do that would be in the Header Customization when we place the background image, just as it is with our foreground image (which you have set to automatically link to our main blog page).
When I try to use the Header Widget - there must be constraints somewhere which are restricting the placement of the right image and pushing the 728px banner off the right of the page. I believe that's what Eric was describing and the style definition you gave above didn't change anything...
I know nothing about coding this kind of thing, but maybe if you could explain how you thought people could/would use this new Header Widget to accomplish that feature request - how it works when you use/test it - we could figure it out?