var xPos = 300;
var yPos = 200;
var step = 1;
var delay = 30;
var height = 0;
var Hoffset = 0;
var Woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
img1.style.top = yPos;
function changePos()
{
    width = document.body.clientWidth;
    height = document.body.clientHeight;
    Hoffset = img1.offsetHeight;
    Woffset = img1.offsetWidth;
    img1.style.left = xPos + document.body.scrollLeft;
    img1.style.top = yPos + document.body.scrollTop;
    if (yon)
    {
        yPos = yPos + step;
    }
    else
    {
        yPos = yPos - step;
    }
    if (yPos < 0)
    {
        yon = 1;
        yPos = 0;
    }
    if (yPos >= (height - Hoffset))
    {
        yon = 0;
        yPos = (height - Hoffset);
    }
    if (xon)
    {
        xPos = xPos + step;
    }
    else
    {
        xPos = xPos - step;
    }
    if (xPos < 0)
    {
        xon = 1;
        xPos = 0;
    }
    if (xPos >= (width - Woffset))
    {
        xon = 0;
        xPos = (width - Woffset);
    }
}

function start()
{
    img1.visibility = "visible";
    interval = setInterval('changePos()', delay);
}
function pause_resume()
{
    if (pause)
    {
        clearInterval(interval);
        pause = false;
    }
    else
    {
        interval = setInterval('changePos()', delay);
        pause = true;
    }
}
start();