title: Responsive web design breakpoints? Why designed for 1280, 1024, 640?
body: <p><em>I received a website layout in Photoshop for three different resolutions: 1280, 1024 and 640 pixels wide. As my experience with RWD is somewhat limited, I would like to get a better understanding of how a web designer should think in terms of size breakpoints, fluidity etc. (at the time of writing).</em></p>
  
  <p>My specific questions, stemming from this project are:</p>
  
  <ol>
  <li>Why would a designer go with these 3 resolutions, given that the project is a typical company website?</li>
  <li>Generally, are these resolutions optimal or should I our ask for others?<br>
    <em>(Wouldn't 1024, 768, 320 make more sense? Or perhaps I should be looking for "natural breakpoints as opposed to canonical?)</em></li>
  <li>How should I think about implementing the 640 layout in regard to iPhone 3 (@320px) and 4 (@640px)?</li>
  </ol>
  
  <p>Thanks for any help.</p>