Great thought about designing for mobile first, and using the default block level styles for the block-level elements in our mobile version since they all already have the 100% width and are, well, block-level. Floating elements is such a part of a site design that we can write less code by starting with Mobile first.
Also a great demo linked: View Responsive Demo using @media and min-width.
Link: Working with media queries and min-width – (http://www.unmatchedstyle.com/news/working-with-media-queries-and-min-width.php?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+UnmatchedStyle+%28Unmatched+Style+%7C+CSS+Design+Gallery+and+Design+Inspiration.%29) from (author unknown) at Unmatched Style
