Deleted Index on Google

Hello all,
i wanna ask a question..
i use wordpress,wp-robot..
so when i create a website (any section health,iphone,cars etc.) i can get about 1k unique visitors in 2 months..its very nice for me..
BUT, google always deletes my indexes..what's wrong ? can you help me for this case ? did u have experienced this problem ? how can i resolve it ? thanks youu every ideas..

i think there is 2 resolves..
- prevent delete indexes
- re-index website wchich deleted indexes

I'm going to guess that G is detecting that you have useless or duplicate content from wp-robot. Do your pages offer any value or anything unique to a visitor?