var g_y = 0;
var g_speedY = 0;
var g_gravity = .4;
var g_elm = null;

function animatePic()
{
    g_speedY += g_gravity; 
    g_y += g_speedY;
    if (g_y >= 0) {
        g_speedY *= -.85;
        g_y = 0;
    }

    g_elm.style.top = Math.round(g_y) + "px";
    setTimeout("animatePic()", 30);
}