var min=10;
var max=16;
function increaseFontSize() {
   var p = document.getElementsByTagName('td');
   for(i=0;i<p.length;i++) {
      if(p[i].style.fontSize) {
         var s = parseInt(p[i].style.fontSize.replace("px",""));
      } else {
         var s = 12;
      }
      if(s!=max) {
         s += 1;
      }
      p[i].style.fontSize = s+"px"
   }
   if(s==max) {
      toggle_increase();
      toggle_decrease();
   }
}
function decreaseFontSize() {
   var p = document.getElementsByTagName('td');
   for(i=0;i<p.length;i++) {
      if(p[i].style.fontSize) {
         var s = parseInt(p[i].style.fontSize.replace("px",""));
      } else {
         var s = 12;
      }
      if(s!=min) {
         s -= 1;
      }
	        p[i].style.fontSize = s+"px"
   }  
   if(s==min){
      toggle_increase();
      toggle_decrease();
   }
}

function toggle_decrease() {
	var p = document.getElementById("text_decrease");
	if (p) { 
        if (p.style.display == "") {
            p.style.display="none";
        }
        else {
            p.style.display="";
        }
    }
}

function toggle_increase() {
	var p = document.getElementById("text_increase");
    if (p) {
		if (p.style.display == "") {
			p.style.display="none";
		}
		else {
			p.style.display="";
		}
	}
}