window.onresize = ChangeFont;

var  Rule = new Array;
  Rule[0] = 24;
  Rule[1] = 32;
  Rule[2] = 18;
  Rule[3] = 14;
  Rule[4] = 24;
  Rule[5] = 24;

function ChangeFont() {

  var TheRule = (document.all) ? document.styleSheets[0].rules : document.styleSheets[0].cssRules;

  var width = (document.all) ? document.body.clientWidth : window.innerWidth;
  var height = (document.all) ? document.documentElement.clientHeight : window.innerHeight;
  if ( height == 0 ) height = document.body.clientHeight;

  average =  ((width/1600) + (height/1200)) / 2;

  for (i=0;i<Rule.length;i++) TheRule[i].style.fontSize = ( Rule[i] * average );
}