Responsive design in iWeb

I am thinking of redesigning my website to make it more "responsive". On iPad the site shows up fine, but I would like to show it nice on smaller devices as well and keep it readable (font size).

Responsive design (chang position of elements in reaction to screen width of the browser) is not really possible in iWeb, since relative pixel positions are not possible. The site is to big (over 200 pages) to start search and replace code before uploading it - a lot of pages are updates almost daily, so it would be to much work to do this outside of iWeb.

I am considering to make a lay-out having the main text and navigation on the left side, and make the page not wider than about 300px - then pictures and less important text would be on the right side but NOT on the page itself but in a picture set as browser background. They would disappear on smaller devices but be visible on bigger devices. Would that be a workable idea or is there a better workaround for responsible design in iWeb?