The others, stop spamming and answering without even reading the topic

Like Keith said above you haven't given us enough information to provide an answer. Of course the real answer is not to worry about it, but since you're looking for a reason why your PR dropped...

Based on the information you've provided I'll go with either Google has a personal vendetta against you or the planets have all aligned in a way to cause your site to lose PR.

Originally Posted by vangogh

Based on the information you've provided I'll go with either Google has a personal vendetta against you or the planets have all aligned in a way to cause your site to lose PR.

Don't think about toolbar PR Ranking is more important..so try to get better ranking

Originally Posted by vangogh

Like Keith said above you haven't given us enough information to provide an answer. Of course the real answer is not to worry about it, but since you're looking for a reason why your PR dropped...

Based on the information you've provided I'll go with either Google has a personal vendetta against you or the planets have all aligned in a way to cause your site to lose PR.

Nice one ...

But yes, there are some spammers out here, look at some answers and you'll know that they didn't even read the topic .. just saw the subject line and dropped a word or two ..

second, I didn't give the website URL, and I asked the question, that means that I'm looking for a general answer .. My question is, what are the main reasons that make Google give such a penalty .. just curious ..

I dont think pr is important, you are getting same traffic thats enough!

that means that I'm looking for a general answer .. My question

The general answer is don't worry about PR, but since you are asking here are a few possibilities of the top of my head.

1. If Google think you're selling links based on PageRank they might have changed your Toolbar PR to 0

2. The links that gave you the PR3 are either no longer linking to you or have been devalued

3. You've crossed some spam line in the eyes of Google. You can test this by seeing if your domain still shows information when typed into Google.

I didn't give the website URL, and I asked the question

Understandable. In the future it would probably result in more quality responses to mention you're just looking for general responses. We get plenty of people asking for specific, detailed answers without supplying the information to get those answers and I guess we mistakenly assumed that applied to you as well.