I am planning to purchase a new domain name. The domain name I am looking for is not available with .com extension as some one has already purchased it but is available with .biz extension. Is it OK to purchase .biz domain?
Depends on what you intend to do with the domain. If you want to resell just the domain then you should avoid the .biz extension. If you want to use it for a website then .biz is fine. However you should know that most people will find it easier to remember a .com, .net or .org domain than a .biz domain.
For yourself its okay to purchase one.. if you're thinking of reselling the domain I wouldn't do it.. I don't think they're very popular.