title: Does "width" overwrite "padding"?
body: <p>Let's say the width of the containing box is 5cm, padding(all sides) is 2cm.</p>
  
  <p>if I set the width of the content to be 50%. Now the absolute value of the width would be 2.5 cm. But if the padding effect is still there, then the box now would be 2+2.5+2 = 6.5cm. But the content would no longer be 50% of width now(2.5/6.5 != 50%).</p>
  
  <p>I'm kinda confused,any help? Thanks!</p>