I developing a client's blog and he needs it to be bilingual (english and spanish). Now what he wants is that users can get to the content based on the domain e.g. Jhon enters www.domain.com and he gets the english version and Juan enters www.elsenordominio.com to get the spanish version. All content will be validated by php so the users and search engines only reads the domain related language. What do i need to use header re-direct or 301? is it bad for seo? will google will google penalize me? I hope you guys can help me and forgive me if my english is not good.