How much do the Dursleys know?

[williaka44]

No: HPFGUIDX 44002

Please excuse me if this has already been addressed here, I am very 
new to the group.  I would like to say that I do really enjoy it and 
it is addicting:-).  I have been listening to the audio version of SS 
(read by Jim Dale), and I have canon to back it up.  In chapter 2, 
the Dursleys are debating about whether to take Harry to the zoo and 
he offers that they could just leave him home.  Petunia replies, 

"'And come back and find the house in ruins?' she snarled."  <snip> 
(after Petunia suggests that they leave him in the car, Vernon 
replies)"That car's new, he's not sitting in it alone." 

What I'm wondering about is what the letter that Dumbledore wrote to 
the Dursleys said exactly.  Obviously Petunia knows that the Potters' 
house was destroyed(she comments about it at a later point, but I 
can't remember where), but do they know why?  Might they know about 
Voldemort and be afraid of the WW because he may come after Harry 
while Harry is in their care?  Is that the reason that they hate 
Harry so much?  I know this is a lot, but I noticed this for the 
first time this afternoon and I started to wonder.  It certainly 
seems to support the idea of the secret-keeper charm having been at 
least conceived at the time of SS if the Dursleys are afraid to leave 
Harry alone.  If anyone has any other thoughts, I'd love to hear them!

-Karla (who thought she was the only person over 18 to like Harry for 
the longest time)