My PR was reduced from 4 to 0, why?

If you are not did any spam. You must be send reconsideration request to Google from Google webmaster account.

 

You are right. You need to work hard in creating more backlinks by doing so posting work on do follow blogs and link exchanges.

 

Your PR dropped from 4 to 0 because ur site would not had enough backlinks.

 

Due to lots of incoming links no outgoing links, may be the lots of spam post by spammers and less content quality and one more less back links

Thanks
Ohanna Web

 

What do you mean by this? I can't really understand your post?

 

Try to get one way theme related links for your site.

 

Make sure that the backlinks to your site are not coming from sites that Google doesn't like.

 

You are very correct. You need to build more strong backlinks to rank higher.

 

Are you spamming? try to build quality link building