I'm trying to use multiple styles but it's not working.

When I link content within an iframe using a different style, (using, &styleid=3 for example) it changes the style to 3 on the next page that's loaded.
Is there a way to use multiple styles without effecting the default style?
So, if I want content within an iFrame displayed using a different style than the rest of my forum, can I do it without changing the users style?
THANKS for reading my issue!