My SERPs for all keywords has fall down in two days ?

I dont know how but on saturday night after checking SERPS for all my 100 keywords i found them on top ten ( 1st page of google) but when today monday morning when i came and check again all manually then all keywords are fall down from 1st page to second page or some are gone 1st to 3rd and 5th position. I dont know how it is possible.
can anybody tell me does google changed its algorithm or my site get penalty ? or any other thing may have been happen which i dont know ? please suggest me, my 70% of traffic are coming from google only. It will be a great great loss to me if it begins to continue. Plaease telll me what should i do to slove this problem.

One more things we have posted in total 30 top bookmarking sites only two urls in each for one a particular keywords foreg for "Diet Information" keywords total 60 backlinks in 25 days. + in three fourms given genuine reply with our domain name links and total url in those all three forums come to 30 url links . so is this due to that google crawler finded all these spaming or anyother reason

 

I've found a few strange things happen with my sites the past seven days

1: Pages taking a long time to get indexed, those which did last week are now not in the index, at all

2: On other sites, there has been slippage on the SERPS

It would appear as if Google is either having an update of sorts, or I'm hitting different data centres.