var max = 24
var min = 8
function upSize() {
    size = parseInt(document.getElementById("bodyInner").style.fontSize)
    if (size < max) {
        size = size + 2
    }
    document.getElementById("bodyInner").style.fontSize = size + "px"
}

function downSize() {
    size = parseInt(document.getElementById("bodyInner").style.fontSize)
    if (size > min) {
        size = size - 2
    }
    document.getElementById("bodyInner").style.fontSize = size + "px"
}