Page not found - Frontend - permissions?

I was working on a site earlier today setting permissions and ACLs and I've just discovered that the site is now down with a 404 page not found error. I can still access the manager though so I'm presuming it's related to the permissions for web context. I've checked everything against a clean install but can't locate the problem.

Can anyone help? I could really do with getting the site back online.

Thanks in advance, apologies if this is an faq, I have done some searching.

Well mysteriously my site is back. I manually cleared the site cache so maybe this had something to do with it. Back to recreating my permissions.