[TheLastSuperman]

That's because the header image if HUUUUUUUUGE @ 1125px x 233px.

I would take a hint from "responsive" web design and use @ media screen css example:

@media screen and (min-width: 1125px) {
     .logo-image {
background: transparent url(images/misc/bannergraphic_photoshop.png);
     }
}

@media screen and (max-width: 1124px) {
     .logo-image {
background: transparent url(images/misc/bannergraphic_photoshop_small.png);
     }
}

Try that in additional.css but change the bannergraphic_photoshop_small to your image smaller logo image needs to be a smaller shrunk down version of your logo i.e. less text etc perhaps just icon/logo only so that way when it resizes your logo is not larger than the content.

I'm actually working on a responsive style now and its giving me some issues on subsequent pages but that should work let me know if not.