synopsis, I need help?

[CountessBathory]

I look on the net to give me tips on creating a synopsis, but nothing is helping. How long are they to be? If my book has lets say 200 pages, how long should a synopsis be? What do I put in it?
I have read on the net that a synopsis is dreaded by most writers and I think I know why...

any help would be great.
synopsis is for my novel I wrote.