DO NOT OPEN IT.
if you don't read it they can't fine you, a bloke told me that the other week when I asked him why he hadn't taken his council issued fine off his windscreen.
I'm reminded of that animal from Hitchiker's...the ravenous bugblatter beast of Traal? The one that you are safe from if you wrap your towel around your eyes because it thinks that if you can't see it then it can't see you and so nothing is there.
If that was true, anyone could park anywhere at any time without any possibility of being fined because they could just throw the notice in a bin without opening it. I think that only works if you have diplomatic immunity.