The quality of incoming links can change daily. It just depends when google updated their pagerank. For example just 1 link to your site from a high pagerank page can have a significant impact and perhaps google updated their PR at just the right time last time it was updated. Mabye now this same link has less much less impact on PR.
There may be many reasons, you way of promoting website, duplicate contents, black hat SEO etc. I think so you must consult to Google then you can know the proper reason and solution for your problem.
Your links are your vote to your sit links-vote to site Once you lost your links, you lost your votes ans automatically your page ranks drop down
I think your keyword is very poor as you use for that site, that's why is down to zero. Another problem may occur that google page rank checker does not work properly on due time.
Without constant upkeep to your site and constant relevant backlinking anything is possible with ggole.
I think so you must contact to Google regarding page rank loss. This is really a seriously matter we should not ignore this matter.
Yeah hussain. but waht should be the reason behind this. There is only the way to know the reason is contact Google directly.