why does Element flickers on scroll

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Javascript

CSS

IE8

chrome

I'm having a feedback box, which has to be at the right corner of the page and should scroll up and down with the scroll bar. But how to stop its flickering in IE and chrome CSS for that div is:

#showSurvey
{
position: relative;
width: 230px;
top: 190px;
float: right;
height: 60px;
}

and javascript to keep it at top is

var wintop = $(window).scrollTop(); if(wintop >= 190) {$('#showSurvey').css('top', (wintop + 10));} else{
$('#showSurvey').css('top', '190px');
}

Using this the div flicker a lot and it looks ugly can anyone please help

javascript css