I put together a responsive wireframe with the help of Axure to show clients what they need consider when they make the off-handed request that a site needs to support mobile browsers. Even with this simple layout, there are still a ton of things to consider especially when it comes to image aspect ratios and resizing. The worst break point for me is the transition between 1024px to 768px. The grid column situation gets tricky. It's not dead on, but close enough for a wireframe.
Note: The iPhone landscape viewport is useless for web browsing so I stuck with the portrait view for both and center aligned everything.
Drag the browser window to change the view.