I have had the good fortune and pleasure of working with one of ZA’s most brilliant SharePoint UX and Front end specialists. We are focusing on responsive design in SharePoint 2010. One of the tricks shown to me was a simple border at the top, with a colour per media query, to help identify whats what.
You have no idea how much time this simple border saves.
I have created a HTML 5 Media Query starter kit. It has the most common sizes, with the border and colour pre set. I hope this helps, and saves you some time 🙂