I'm new to the forums so please excuse any incorrect placement of this thread...
I've just installed Xubuntu on one of my laptops and the first site I tried was American Express (Australia) and I can't login due to an error on the page.
I installed Chromium as well and had the exact same problem. I imagine this is an issue with the OS... short of Amex fixing their website (had no issues in Windows or OSX on this site).
When you go to the page (https://www.americanexpress.com/australia) there's a login box at the top left, a "business" button is incorrectly placed and you can't use the login.
The Amex US site doesn't have the issue. In fact, I just figured out I can login to the US site, I guess this is still an issue though.