/*
This function opens a window centrally
*/
function show_window(htmlFilename,windowWidth,windowHeight)
{
	show_image_window = window.open(htmlFilename, 'showImageWindow', 'width='+windowWidth+', height='+windowHeight+', top='+((screen.availHeight/2)-(windowHeight/2))+', left='+((screen.availWidth/2)-(windowWidth/2))); show_image_window.focus();	
}