title: CSS performance: Is that Using percentages slower than Using pixel
body: <p>My question is as the title. Please answer me.
  I am developing a website. I would rather use percentages than pixel, because it's flexible, everything keeps same ratio despite of the width of browser.</p>
  
  <p>But what I concern is: <strong>when we using percentages, is that the browser will make alots of calculation?</strong> Do it compute <strong>"1% approximate to ?px"</strong>? If that I think the loading will be slowed down.</p>
  
  <p>Please answer me. Thank you alot!</p>