Lately lots of major website was faced with page rank drop. Not to mention it affected the blogs network too. Some reduce from 5 -> 3, 4->2..etc. Now how does Google calculate and rank your website. I must say it is a complicated algorithm or formula. However, I bet there are human intervention too because there are sneaky and smart people who find ways to abuse the system.
Let me make it simple for you especially for those who do not have any clue about page ranking.
Google page ranking is dependant on a few factors like content, traffic, back links, outgoing links and other stuff put together. Content is basically what you write. If you write good content, people will link to you and by linking to you, other visitors may drop into your site to read your content. If you have many people visiting your site, that is call traffic. Traffic produces good ranks but this is not just it.
When other site link to you, it is call back links. Back links are very important to increase your ranks. Example if your site has lots of rank 4 sites linking to you, your site will eventually be rank 4. If you have lots of rank 3 sites linking to you, most likely you will be rank 3.
Outgoing links are the links you create on your site. The more link you have, the rank will be affected greatly. Therefore, link smartly. Links include paid links and other links too. You do want to link to other sites so that you can share with others your rank. By the way, I found that there is couple of bloggers who removed their links or blog roll which makes me think that they do not want to share ranks with others.
By the way, page rank is tie to the page and not entire domain. Some pages you get rank and some you don’t. If a blogger link to you using his/her PR 0 page, it means he/she is sharing PR 0 with you. Be smart.
There are things you should avoid doing and it is a BIG NO NO that Google will penalize you big time for it. Do not participate in any linking activities such as link farm or tags of linking to a whole bunch of people you do not know. I saw a lot of those kinds of tags and it does not help with your PR. Do not create post with bogus keywords or have hidden texts or links.
Lastly, do housekeep your sites with links and link smartly. Hope you have a good rank!