Grab the corner of your web browser and make the window bigger or smaller – you will see the site layout change as you go from full width to mobile width of 320px.
Got an iPad, iPhone or a recent Android or Blackberry? If not, ask (nicely) to borrow one and load this website to see how it renders nicely. No pinch to zoom needed.
Now try rotating the smartphone or tablet and watch the site adapt to a different orientation. This is exactly what you would need!