ok my google pr fell down to 0 a couple of days ago. but i check my analytics todays and traffic is pretty much the same along. and all pages are indexed too. i thought pr 0 means your ranking in serps is very low? or pr has nothing to do with this? thanks.
Pagerank and SERPs are two seperate things. Pagerank is the popularity of your site based on backlinks from other sites. SERPs is your position for keyword\phrase in the search engine. Your pagerank can drop and NOT effect your SERPs. Pagerank drops if your backlinks lose pagerank due to selling text links, or just not linking back to your site anymore.
Stop bothering yourself with PR. You can get PR as long as you get backlinks in google. While waiting for your PR concentrate more in improving your SERP. As long as you don't stop in getting backlinks you can have PR on next PR update.