<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.js"></script>
<script type="text/javascript">jQuery.noConflict();</script>
<script>
$(document).ready(function(){
$(window).scroll(function(){
var scrollTop = $(window).scrollTop();
// now on the basis of scrollTop value show your div
if(scrollTop > 1){
$('#PopupSignBut').fadeIn('slow');
}
})
});
</script>
What jquery jquery.js library should I use? I only need for this code and kind of would like to use small file size?
No. Have a look at the example in the linked page.
As usual, that depends … the less older browsers you have to support, the better.
For getting the scroll-top it would probably suffice to have a look at the relevant jQuery source code.
The animation is more complicated (and–again–browser dependent). It’s possible to achieve that using CSS transitions or maybe use a more specialised animation library.