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It is not that you got discriminated. They use different algorithms plus Google has recently updated their core algorithm by combining it with Panda (the On-Page algorithm).  This has caused a lot of fluxuations last month and I am still seeing some movement.  I would focus on ranking on Google based on the fact that they have approximately 80% of the Search Engine Market share.

Hi Patrick, Thank you for your opinion. it will be very helpful. i will try more SEO job like you said.

Thanks for your information. i am still questioning about that there is no SEO job, but only internal link can the keyword on 1st page? the site is nothing in terms of SEO factor, except internal link though.