bild in div vertikal zentrieren

[MudGuard]

Hi,

müßte nicht auch
#header img {
margin: auto 0 auto 0;
}
funktionieren?

Nein, wegen:

10.6.2 Inline, replaced elements block-level, replaced elements in normal flow, and floating, replaced elements

If 'top', 'bottom', 'margin-top', or 'margin-bottom' are 'auto', their computed value is 0. If 'height' is 'auto', the computed value is the intrinsic height.

http://www.w3.org/TR/REC-CSS2/visudet.html#Computing_heights_and_margins

cu,
Andreas