Languages in webpages and iFrames

I was wondering if there is any html tag you can slip in at the beginning of the webpage to change the language. I'm not talking like geo targeting where it automatically reads the IP and sends to a page in a language, I'm talking like a tag maybe from a translation website that will automatically translate pages?

Also is there a tag for iframes where you can set a language and it automatically changes the form's language?

Or am I thinking wayyy too out the box. heh