Problems with Opera 9.50 with the layout..., ...as a guest here - BIG PICS WARNING!!!

I have a "little" Problem with the layout of the Website when I visit it as a guest. I`m using Windows XP with Service Pack 3 and the Opera-Browser in the version 9.50. I also tested it with Firefox in the Version 3.0-I think it was the RC2, but I´m not sure anymore.

Here are some screenies to compare:

Opera:



FireFox



Can somebody help me, please?

How did you get Opera Mini for Widow$?

Try fiddling with settings. I'm not sure, but there may be some mobile view settings. (I've heard of some.)

Works fine for me, but I'm using Vista Sp1. Have you got Fit to Width turned on, that sometimes throws a wobbly. (Untick View>Fit to width)

No, it is deactivated, and with activated "Fix to width" it looks even worse.
And I have activated now the, I think it is named "Error Console" in english, in Opera, and it showed some interesting stuff:

So, is it just Opera or a bit of bad written HTML-code which all the other browsers could fix by themself? I dunno, I only know BASIC, but not HTML.

Well, however, as long as it looks normal when I am logged in, it´s near to fine, but what `bout the guests who uses Opera?
I have tried everything with the settings in Operas Style settings.