var min = 0.5;
var max = 2.5;

function increaseSize()
{
   var p = document.getElementsByTagName('p');
   for(i=0; i < p.length; i++)
   {
      if(p[i].style.fontSize)
	  {
         var s = parseFloat(p[i].style.fontSize.replace("em",""));
      }
	  else
	  {
         var s = 1;
      }
      if(s < max)
	  {
         s += 0.25;
      }
      p[i].style.fontSize = s+"em"
   }
}

function decreaseSize()
{
   var p = document.getElementsByTagName('p');
   for(i=0; i < p.length; i++)
   {
      if(p[i].style.fontSize)
	  {
         var s = parseFloat(p[i].style.fontSize.replace("em",""));
      }
	  else
	  {
         var s = 1;
      }
      if(s > min)
	  {
         s -= 0.25;
      }
      p[i].style.fontSize = s+"em"
   }   
}