'can't connect to server' message

I'm not very computer savvy so please, no super technical answers : )
I downloaded Maverick without any problems (I had the correct prerequisites on my 2011 Macbook Pro) but now I can't sign in to various sites i.e. I can connect to Amazon.com but when I try to sign in, I get a 'can't connect to server' message; the same with ebay.com, iCloud, ibook, and so on. The help button doesn't give me any info.
Router working fine in internet surfing, just no luck signing in to sites.
Suggestions? Thank you.

 

I can't enter my password--that's the problem.
When I click on 'sign in' on Amazon.com or ebay.com, etc, instead of going to the screen where I can enter my password, there's a screen that says 'can't connect to server'.
Thanks for replying, though.