I know that this is pretty stupid question, but does anybody know any site where one can find general plans and ideas in  openings,  explained? Thanks.

http://en.wikipedia.org/wiki/Chess_opening

thanks, but this is not what I ment. I think this can not be find on the internet...

well I think the Wiki page does quite well in explaining the general opening principles and summarizing the various categories of openings.

Maybe you should buy this book then:

http://www.amazon.com/Ideas-Behind-Chess-Openings-Algebraic/dp/0812917561/ref=sr_1_1?ie=UTF8&qid=1248382548&sr=8-1

It's a bit dated but still considered a classic.

this site, "openings",  any of the billion chess books on openings and opening theory, the internet search engines, opening chess theory, reuben Fine wrote a classic on the openings dealing with your very question....

I just memorize a lot of openings, that is probably why my chess960 rating is so low, sigh, need to work on the endgame :(...Anybody have good articles on that?

not me, sorry

A few recent books have tried to do this (Fine's book is said to be very outdated):

John Watson's "Mastering the Chess Openings", parts 1-3

Djuric's "Chess Opening Essentials", volumes 1-3

I would guess that Watson's is more suitable for slightly more advanced players, but I haven't read any of these books.