If you're using the SSL connection you may get a red bar appear in internet explorer and a screen in Firefox and Crome that indicates that it is untrusted.
It's not, just add an exception and carry on as normal. I'm just a bit lazy and haven't renewed the security certificate yet.
If you don't use SSL (that's https:// by the way
) ignore this post 
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Edit: Like my cat, this is all fixed now.
However this may, or may not happen again next year, it depends just HOW lazy I am
