Hi, I came to the US on the last week of Sept 2009 on L1 visa for the period of 3 months. I am getting my india salary credited into amy account and I am getting 40$ per per diem for the stay in US. I haven't got any offer letter, pay salary etc from my US based subsidiary comp of indian comp. I haven't applied for SSN yet. I don't know how my tax will be paid at US. So please tell me is my stay here at US on L1 visa will be termed as illegal? Will I face any trouble on my next trips to USA. Please tell me how should I go for this?

If you entered US on L-1 visa, there's nothing to worry about. Ask your employer or their attorney about documents needed for taxes, legal status, etc.