Google traffic drop

[photogold]

The traffic I get from Google has dropped by about 80% over the last month. Has Google changed its algorithms recently ? I still get traffic from Google but all my rankings on my keywords seem to have got much lower . I used to get over 1,000 visitors a day.
My site is www.castlepictures.com . Can anyone suggest an approach I can use to find out what has gone wrong ?

[google junky]

Which keywords are you worried about that have lost you ranking? You come out #1 for the search for castle pictures

[Jade456]

It might be due to the time of year. I know our traffic has dropped but our serps have not. Could be that more people are on vacation, etc than surfing the web.