[xmonad] gap between window and statusbar (xmobar)

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Hello Guys!

I'm relatively new to xmonad (and Haskell), so this might be a stupid question. But well, I'll shot it anyhow ;)

In my config (see below), I have to xmobar's running, one on top with only %StdinReader% and the second on bottom with MPD and Date. The xmobar on top has as Border on Bottom and the xmobar on .. you 
guess it. Well: while the borders of my windows and the xmobarborder sort of merge (1px + 1px = 2px), there is a gap between the borders of my windows and the xmobar on top. Why is that so and what can 
I do about it? 

Here is my xmonad.hs: http://hpaste.org/65398

(Oh, I see it's complaining about redundant $'s and that I should use 'head' ... what does the latter mean?)

Greetings from sunny Cologne,
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