RWD: different devices exhibit the same page

With the popularity of 3G, more and more people use the mobile Internet. Mobile devices are more than desktops, the most common terminal to access the Internet. So, web designers have to face a dilemma: how to render the same page on different sized devices?
The phone's screen is relatively small, usually 600 pixels width or less; PC screen width of 1000 pixels or more generally in the (mainstream width is 1366 × 768), and some reached 20 pixels. The same content to different size on the screen, show satisfactory results, not an easy task.

Many solutions website is to provide different pages for different devices, for example, specializes in providing a mobile version, or iPhone / iPad version. This of course ensures results, but too much trouble, while maintaining several versions, and if a site has multiple portal (entrance), will greatly increase the complexity of the architecture design.

Thus, it has long been contemplated, can "design once, universally applicable," so that the same page automatically adapt to different screen sizes, according to the width of the screen automatically adjusts the layout (layout)?