I am working on a CMS which makes use of IFRAMEs to display some forms, for illustration, say a Search form. So the user clicks the Search button and the website reacts by opening a popup window which includes an IFRAME to the actual Search form.

This means I have a "bare"¹ page with the search form. Page which, obviously, is directly accessible via its own URI.

In terms of SEO, the forms have no content worthy of being indexed, so I was thinking to mark them as NOINDEX. Is that the correct way to handle such pages?

From what I read on some other question, Google suggests to put links from IFRAMEs to other pages. However, I definitively do not want a user visible link to the Home page, or whatever page in link with the form, in the content of my forms because that could be misinterpreted by the user. However, if <link> tags would work too, which one should I use? (i.e. "top" would work, right? with the home page in there?)

¹ By bare I mean that the normal theme is not show, it will be a plain white background with just and only the simplest form.