I need to know if we can have multiple adsense code, with different adsense account on one website.
Suppose I sign-up with google with 2 diffenrent IDs, and put 2 diff. code on a single website.

Does google permit such thing or they dont care about multiple adsense code?

The 1st problem here is: how come you'll have 2 adsense account?! Just a piece of advice: stick to Google Adsense TOS to avoid getting ban.

This is what i know about this: Normally publisher can keep only one account but in special times i mean reasonable situation publisher can keep two accounts
One for personal and other one for business .

In this case publisher want submit a new application.on that application publisher should want to select the account type individual or business.If he has individual account then he can apply for a new business account.