Inger, I took a look at your site on my Dell Mini (Linux-Ubuntu), latest Firefox version. The flash object covers the headings. It has a white background rather than the transparent background i see when viewed on my Windows pc (latest Firefox version). When I clicked the link to your site I saw the headings "flash" for a split second before the Flash covered them up. Everything is there - but underneath the Flash. (maybe something to do with z indexes ?)
I don't know enough about html/css to offer any advice (VSD user here), just wanted to let you know how it was "misbehaving" on another Linux computer. I do have the Web-Dev toolbar on there, so if there's anything you would want to look at, I can check it out and report back to you (screenshots if needed) so you can compare it with what you've got there.
Hopefully someone else with some Linux knowledge will come along with a really simple answer to this, but I don't mind sending on any info I can if you don't get a quick fix and need to explore some more options.