If you click on the logo, or go directly to mumsnet.com you go to a blank page that says "Welcome to nginx!" rather than the home page.
I go directly to Active Conversations so it doesn't affect me that much, but it'll mess up anyone searching for the site I'd have thought?
Apologies if it's not happening to anyone else, it might just be AdAware giving me problems (it's been doing odd stuff with MN today!)