$(window).scroll(function(){
$("#your_block").css({"margin-top":$(this).scrollTop()});
});$( ".modals" ).click(function() {
$( ".main" ).css( "-webkit-filter", "blur(5px)" );
$( ".modalDialog" ).css( "background", "rgba(0,0,0,0.8)" );
$( "html" ).css( "overflow", "hidden" );
$( ".main" ).css( "transition", "0.5s" );
});