[alilg]

Okay, just replace this function

function update_tip_pos(){
        document.getElementById('ToolTip').style.left = mouse_X + 20;
        document.getElementById('ToolTip').style.top  = mouse_Y;
}

with this which i wrote

function update_tip_pos(){
        document.getElementById('ToolTip').style.left = parseInt(parseInt(mouse_X) + 20) +"px";
        document.getElementById('ToolTip').style.top  = mouse_Y + "px";
}

let me know it worked or not!
i tested if with firefox 2 and firefox beta 3