var speeda = 20;
var tabaLeft = document.getElementById("demoLeft");
var taba1 = document.getElementById("demo1");
var taba2 = document.getElementById("demo2");
taba2.innerHTML = taba1.innerHTML;

function Marqueea1() {
    if (tabaLeft.scrollLeft >= taba2.offsetWidth)
        tabaLeft.scrollLeft -= taba1.offsetWidth
    else {
        tabaLeft.scrollLeft++;
    }
}

var MyMara = setInterval(Marqueea1, speeda);

tabaLeft.onmouseover = function () { clearInterval(MyMara) };
tabaLeft.onmouseout = function () { MyMara = setInterval(Marqueea1, speeda) };