title: Best standard Image Sizes for different width of screens for website
body: <p>I am using picturefill.js library to pull up same image with different sizes on different width of screen.</p>
  
  <p>Dilemma is that what should be the number of images should I create by keeping in mind of all mobile, tablet, desktop ? 
  By doing this I want to save bandwidth.</p>
  
  <p>Right now, I am creating same image with with different below sizes. Size of images are in pixels</p>
  
  <pre><code>240   
  320 
  640   
  480 
  600 
  768 
  960
  992
  1200
  1368
  1600
  2400
  2500
  3200
  4000
  </code></pre>
  
  <p>If I create image with this all sizes and load it using picturefill JS, will it have any effect on performance ? </p>