Thanks for trying to help me!
That worked on the empty page, but I still have the problem when embedding it. I've put the "body margin 0" in both the css-file and in the header of the html-file (haven't uploaded it though).
The strange part is that the scrollbar disappears when I put the 'huvudprojektbilder' <div> at the top (top: 0px; in the css-file). If I just put '1px' there, the scrollbar pops up, and the same thing happens if I remove 'huvudprojektbilder' <div> completely and for example put an <br> before the sv-code. But if I set the distance to 0px and change the height in the sv code from 570 to 670, the scrollbar is still invisible. I succeeded in fooling it by adding 100 to every Y-value in the Fixed layout-section, and also adding 100 to the total height. In that way, the whole gallery is lowered and the scrollbar is still invisible. Put the problem then is that the white area at the top of the gallery covers my top menu and logo (even if the 'huvudprojektbilder'-div is set to the lowest Z-value). I haven't uploaded this changes, but just name it and I will.