$("#screenshot")
.css("top",(e.pageY - xOffset - 300) + "px")
.css("left",(e.pageX + yOffset) + "px")
---------------
var bDefective = (screen.width <=1024 && e.pageX > $(window).width() / 2);
$("#screenshot")
.css("top",(e.pageY - xOffset - 300) + "px")
.css( bDefective ?"right":"left", e.pageX + (bDefective?-1:1) * yOffset) + "px")