It works now on firefox and ie but on firefox it is too sensitive but background-position is now good
$('#pageBg').mousemove(function(e){
var mousePosX = (e.pageX/$(document).width())*100;
var mousePosY = (e.pageY/$(document).height())*100;
$('#pageBg').css({
'background-position': mousePosX +'%' + mousePosY +'%'
});
});
EDITED: You have to change window => document/width/height . Firefox counted not right mousePositions as other browsers do. So there's to way to fix it or leave (window) and detect browser (firefox) and then
var mousePosY = (e.pageY/$(document).height()); //without 100
Or change (window) for (document) and it works on Chrome, Opera, Firefox, IE, Maxthon and Safari. Smooth as it should for me.