var currentpos=0;
var dir=0;

function setup(){dir=-5;}
function setdown(){dir=+5;}
function setzero(){dir=0;}


function doscroll(){
if(navigator.appName == 'Netscape') {currentpos=window.pageYOffset+dir;}
else {currentpos=window.document.body.scrollTop+dir;}

window.scrollTo(0,currentpos);
}

setInterval("doscroll()",5)