title: Pixels in CSS vs pixel density
body: <p>I am incredibly new to HTML and CSS and it just occurred to me that when deciding something is 5px say, since a pixel's physical size is dependent on the density then surely 5px on a screen of 100 ppi would look bigger than on a screen of 300 ppi.</p>
  
  <p>Is this correct and if so is there any way to mediate this?</p>