function fontUp()
{
    var currentNum=document.getElementById("SubContentContainer").className;
    currentNum = parseInt(currentNum.replace("SubContentF",""));
    
    if(currentNum < 5 ){
        document.getElementById("SubContentContainer").className="SubContentF" + (currentNum + 1);
        document.getElementById("FontDown").style.color = "#fff";
    }
    if(currentNum+1 == 5)
        document.getElementById("FontUp").style.color = "#ccc";
  
}

function fontDown()
{
    
    var currentNum=document.getElementById("SubContentContainer").className;
    currentNum = parseInt(currentNum.replace("SubContentF",""));
    if(currentNum > 1 ){
        document.getElementById("SubContentContainer").className="SubContentF" + (currentNum - 1);
        document.getElementById("FontUp").style.color = "#fff";
    }    
    if(currentNum-1 == 1)
        document.getElementById("FontDown").style.color = "#ccc";    
}