I have a message in the header I display throughout the site as well as a lot of content in list format in my right sidebar.

After hearing about these horror stories of google punishing for OOP, punishing for duplicate content, punishing for overdoing keyword density, seeing my sidebar list end up in meta description results and google preferring more sentencey format over list format for keywords in general this has me nervous about my boilerplate content.

My understanding is that google recognizes boilerplate/template content anyways and doesn't count it that much when it comes to SERP's for keywords?

So can't I just put header and sidebar content into iframes to clean up my main content or could this hurt me as far as SEO? It would dramatically decrease the page size which should help googlebot make more frequent visits as well, right?