var min=9;
var max=15;
function increaseFontSize() 
{
   var p = document.getElementsByTagName('*');
   for(i=0;i<p.length;i++) 
   {
      if(p[i].style.fontSize) 
      {
         var s = parseInt(p[i].style.fontSize.replace("pt",""));
      } 
      else 
      {
         var s = 11;
      }
      
      if(s<max) 
      {
         s += 1;
      } 
      
      if (p[i].className != "font_size")  p[i].style.fontSize = s+"pt"
   }
}

function decreaseFontSize() 
{
   var p = document.getElementsByTagName('*');
   for(i=0;i<p.length;i++) 
   {

      if(p[i].style.fontSize) 
      {
         var s = parseInt(p[i].style.fontSize.replace("pt",""));
      } 
      else
      {
         var s = 11;
      }
      
      if(s>min) 
      {
         s -= 1;
      }
      if (p[i].className != "font_size") p[i].style.fontSize = s+"pt"
   }   
}