$(function() {
$(window).scroll(function(){
var scrollTop = $(window).scrollTop();
if(scrollTop != 0)
$('#headerTop').stop().animate({'opacity':'0.2'},400);
else
$('#headerTop').stop().animate({'opacity':'1'},400);
});

$('#headerTop').hover(
function (e) {
var scrollTop = $(window).scrollTop();
if(scrollTop != 0){
$('#headerTop').stop().animate({'opacity':'1'},400);
}
},
function (e) {
var scrollTop = $(window).scrollTop();
if(scrollTop != 0){
$('#headerTop').stop().animate({'opacity':'0.2'},400);
}
}
);
});