For paywalled and other paid content sites, deliverability is an important determinant of success. There’s nothing worse than having a beautifully designed mobile site, only to discover the majority of viewers are accessing your site from an iPad or Kindle Fire.For that reason, a lot of the technorati are touting responsive web design as the solution to ever-changing platform sizes. (If you think you’re all covered with sites optimized for desktops, laptops, mobile, tablets, iPads, and the Kindle, you’re still not ahead of the curve. Industry predictions are favoring televisions and gaming systems as the next trendy content delivery systems — and those Google glasses are bound to be the next rage.)Responsive web design, in a nutshell, uses CSS programming with fluid proportion-based grids to adapt the content to the viewing platform (for some wonderful design examples, check out Media Queries’ portfolio).However, be careful that your design aspirations don’t cloud your revenue-generating goals. As I wrote about previously on this blog, The Boston Globe has used responsive web design to create an award-winning site, yet remains behind the Dallas Morning News in conversion and online subscription dollars. In fact, the Dallas Morning News is able to convert 49,000 visitors to paying subscribers by using simple PDF technology.Which doesn’t mean responsive web design is a bad idea for your site — especially if your traffic is coming from a variety of platforms. Just make sure your price points and conversions tactics can support your design costs.