Background / colors etc: Preview does not match Edit

Background / colors etc: Preview does not match Edit

Hi,

When I preview my site, background image and colors are *not* the ones I have defined using the Visual Editor in Edit mode, but the default background / colors of the theme

Edit mode: http://imageshack.us/a/img854/6792/editmode20130306232347.jpg
Preview mode: http://imageshack.us/a/img839/4044/previewmode201303062323.jpg

Please note that I have not changed anything in Visual Editor settings since my last publish.

How can I be sure what the site will look like when I publish my changes?! I don't click "Publish" due to this uncertainty.
Is there anything I can check? Is there a fix for this behavior?

Thanks in advance.