Created attachment 442995 [details] This ist a browsershots.org-View of my page. Unsing the page browsershots.org, I've made some screenshots of an article of my page. http://browsershots.org/http://devsup.de/artikel/manipulative-meinungsumfragen Two FF-pages don't show any content. This is a valid xhtml-strict page.
Looking closer at those screenshots it looks like the browsers were still trying to connect to the site and didn't actually complete before the screenshots were taken.
Contact browsershots.org about it
Browsershots shouldn't really be used to find bugs in browsers, as there are too many uncontrolled variables, such as pages not loading, what is in the profile, etc. If you have access to a computer than is running the most recent ubuntu with the most recent Firefox, then we can try to diagnose.