I have a 13 month-old PR 3 Travel site. It ranked well in Google 1st page for some of the keywords. Last month, the SERP for these keywords dropped and went to nowhere. After one week, the SERP returned to normal with some improvement. Two days ago, it dropped to nowhere again. I did SITE: with Google and the pages are still indexed. The number of pages indexed were dropped from 4000 to 3000. There was no major activity made in the last few days. I only added 2 new pages and submitted it to a few directories listed in DP forums. What could possibly happen? Google update again or Penalty? Submitted to a bad directory? Anyone suggestion on what I can do?