$(document).ready(function() 
{
	var height=$("document').ready(function(); //declair variable container "height" and set equal to "document"
	var imageHeight=$("img").height();         //decclair variable "imageHeight" and set equal to "img" 
	
	$('img#myimage').css({"position" :"relative", "top" :height/2 - imageHeight/2})
}