var text="scroll";
var lft = 10; // (window.screen.width/2);
var pos = 10;   // initial top position
var stp = 1;    // step increment size
var spd = 10;   // speed of increment
var upr = 2;  // upper limiter
var lwr = -2;   // lower limiter
var tim;         // timer variable
function scroll_up() {
if(pos > upr) pos -= stp;
do_scroll(pos,text);  
tim = setTimeout("scroll_up()", spd);
}

function scroll_dn() {
if(pos < lwr) pos += stp;
do_scroll(pos,text);
tim = setTimeout("scroll_dn()", spd);
}

function do_scroll(pos,text) {
document.getElementById(text).style.top = pos+"px";
//document.getElementById("scroll").style.top = "200px";
}

function no_scroll() {
clearTimeout(tim);
}