container = "main";
var factor= 100;

// on load test if size changed in any page and maintain it
function maintainFont()
{if (window.name != "")
    {factor = parseInt(window.name)
      // check valid number range
      if (factor > 79 && factor <201)
         {document.getElementById(container).style.fontSize = factor + "%";}
     }
}
// choose size code to alter text for container
function changeFont(size)
{  switch (size)
  {case 1: if(factor>80){factor -=10};
             document.getElementById(container).style.fontSize = factor + "%";  break; 
    case 2:if(factor<200){ factor +=10};
              document.getElementById(container).style.fontSize = factor + "%";  break;
    case 3: factor =100;
              document.getElementById(container).style.fontSize = factor + "%";  break;  
    default: break;
   }
window.name = factor.toString(); 
}