var min = 8;
var max = 18;
function increaseFontSize() {
    var p = document.getElementsByTagName('div');
    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;
        }
        p[i].style.fontSize = s + "pt"
    }
}
function decreaseFontSize() {
    var p = document.getElementsByTagName('div');
    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;
        }
        p[i].style.fontSize = s + "pt"
    }
}