OK, here is the scoop in a more visual fashion. You’re having multiple problems, and they should be addressed in the following order.
I’m placing a link to an image to show you what I’m talking about (click with a scroll wheel to open in a separate tab).
I took several screen captures with a firebug highlighting the offending areas. On the left you can see that the banner has 8px of padding applied to its parent <td> tag, and on the right there is only 1px applied to its parent <p> tag (purple stuff)
First order of business would be to place the banner inside the same container across the entire site. There is no reason why you should have the banner sitting inside <td> on one page, and floating freely on the other (probably the reason for the <p> tag in a first place)
This will either get rid of the extra space (yellow stuff) that is inherent to the <p> tag, or get rid of the extra padding that seems to be applied to <td> (depending on whether you decide to nest the banner inside the table cell or not)
All of your padding and margins are applied through CSS. So if you’re having different results on different pages, it because elements aren’t sitting in common wrapping tags
Now, the orange thing at the top is the other thing that is of concern. On the left, you’re seeing a margin of 8px applied to the <body> tag, but on the right it seems that the padding of 1px is applied to the entire <html> tag. I never formatted html tag with css, but I see no reason why it wouldn’t work, so I guess it’s possible that’s what’s going on. You’ll be able to see what’s going on once you take a look at your css.
One thing I can tell is that if you’re indeed having the entire <html> tag formatted with css, it looks like you have separate stylesheets for blog and for the rest of the site (or else you’d see the same thing across the entire site)
Not sure how much work you put into getting this look set up, but if it’s not too late, I’d say check out the Atahualpa theme. It’s a free theme with customization capabilities you won’t find even in most premium themes, and the guys that made it even have a very active forum built around this theme (it’s the only theme I use).
That theme will solve all of the problems as far as the formatting goes across multiple pages
The only thing is that you’ll have a bit of learning curve to go through as this theme easily have 200+ options. But on the upside, I haven’t found a look that couldn’t be created with it
If not, you’ll just have to find a manual way to fix the issues above.
At least now you know where to look