var min=12;
var max=16;

function resize(tag_element, changesize)
{
    for(i=0;i<tag_element.length;i++)
    {
        if(tag_element[i].style.fontSize)
        {
            var s = parseInt(tag_element[i].style.fontSize.replace("px",""));
        }
        else
        {
            var s = 12;
        }
        if (((changesize > 0) && (s != max)) ||
            ((changesize < 0) && (s != min)))
        {
            s += changesize;
        }
        tag_element[i].style.fontSize = s+"px"
    }
}

function increaseFontSize()
{
    var p = document.getElementsByTagName('p');
    var li = document.getElementsByTagName('li');
    var span = document.getElementsByTagName('span');
	var td = document.getElementsByTagName('td');
    
    resize(td, 1);
	resize(p, 1);
    resize(li, 1);
    resize(span, 1);
}

function decreaseFontSize()
{
    var p = document.getElementsByTagName('p');
    var li = document.getElementsByTagName('li');
    var span = document.getElementsByTagName('span');
	var td = document.getElementsByTagName('td');
    
    resize(td, -1);  
    resize(p, -1);
    resize(li, -1);
    resize(span, -1);
}