excuse my English I speak Spanish

I'm trying to display multiple php and mysql registration, after that the show in an iframe

the problem is that apparently in the iframe shows me errors accents and other characters for example: for example (?D?nde cuesta menos y se consume m?s?")

this is what shows (?)

In the original query or first does not show me that, but in the iframe shows me that error

and probe with http-equiv = "content-type" and I worked

What else I can do?

What should I do?

regards