document.onmousemove=mouseMove;
var firefox=document.getElementById&&!document.all;

function mouseMove(e){ if (firefox) { posx = e.clientX; posy = e.clientY; } else { posx = event.clientX; posy = event.clientY; } }
function show_coverpreview(i) {
    document.getElementById("coverpreview"+i).style.left  = (posx+15) + "px";
    document.getElementById("coverpreview"+i).style.top = (posy+0) + "px";
    document.getElementById("coverpreview"+i).style.visibility = "visible";
}

function hide_coverpreview(i) {
    document.getElementById("coverpreview"+i).style.visibility = "hidden";
}